Chapter IX: Part I (4)

That industrial carbonic oxide poisoning is not rare the reports of the certifying surgeons in Great Britain sufficiently show. In the year 1906 fifty-five persons are referred to as having suffered, with fatal issue in four. In 1907 there were eighty-one, of which ten were fatal. Of the 1906 cases twenty resulted from inhalation of producer, Mond, or suction gas, sixteen from coal gas (in several instances containing carburetted water gas), seventeen from blast furnace gas, and one each from charcoal fumes from a brazier, and from the cleaning out of an oil gas holder.

As causes of the poisoning from suction gas were (1) improper situation of gas plant in cellar or basement, allowing gas to collect or pass upward; (2) defective fittings; (3) starting the suction gas plant by the fan with chimney valve closed; (4) cleaning out ‘scrubbers’ or repairing valves, &c.; (5) defective gasometer. In the seventeen cases due to blast furnace gas six were due to conveyance of the gas by the wind from a flue left open for cleaning purposes into an engineering shed, two to charging the cupola furnace, two to entering the furnace, and four to cleaning the flues.

The following are instances taken from recent literature on gas poisoning[1]: Several cases of poisoning by _water gas_ occurred in a smelting works. The poisoning originated when a blowing machine driven by water gas was started. Owing to premature opening of the gas valve two men employed in a well underneath the machine were overcome. The attendant who had opened the valve succeeded in lifting both from the well; but as he was trying to lift a third man who had come to his assistance and fallen into the well he himself fell in and was overcome. The same fate befell the engineer and his assistant who came to the rescue. All efforts to recover the four men by others roped together failed, as all of them to the number of eight were rendered unconscious. With the aid of rescue appliances (helmets, &c.) the bodies were recovered, but efforts at artificial respiration failed.

A workman was killed by _suction gas_ while in the water-closet. It appeared that some time previously when the plant was installed the ventilating pipe between the purifier and motor, instead of being led through the roof, had been led out sideways on a level with the floor immediately above the closet.

In another case the suction gas attendant had taken out the three-way cock between the generator and motor for repairs and had not reinserted it properly, so that when effort was made to start the motor this failed, as gas only and no air was drawn in. The motor was thought to be at fault, and the fan was worked so vigorously that the gas forced its way out through the packing of the flange connections and produced symptoms of poisoning in the persons employed.

More dangerous than suction gas plants, in which normally no escape takes place, are installations depending on gas _under pressure_. Such an installation was used for heating gas irons in a Berlin laundry. The arrangements were considered excellent. The gas jets were in stoves from which the fumes were exhausted. The gas was made from charcoal and contained 13 per cent. of hydrogen. No trace of carbonic oxide was found in the ironing room on examination of the air. After having been in use for months the mechanical ventilation got out of order, with the result that twelve women suffered severely from symptoms of carbonic oxide poisoning, from which they were brought round by oxygen inhalation. The laundry reverted to the use of illuminating gas. The conclusion to be drawn is that installations for gas heating are to be used with caution.[2]

Industrial poisoning from _blast furnace gas_ is frequent. Two fatal cases were reported[3] in men employed in the gas washing apparatus. They met their death at the manhole leading to the waste-water outlet. In another case a workman entered the gas main three hours after the gas had been cut off to clear it of the dust which had collected. He succumbed, showing that such accumulations can retain gas for a long time. Steps had been taken three hours previously to ventilate the portion of gas main in question.

A fatal case occurred in the cleaning out of a blast furnace flue which had been ventilated for 1½ hours by opening all manholes, headplates, &c. The foreman found the deceased with his face lying in the flue dust; both he and a helper were temporarily rendered unconscious.

Cases of poisoning by _generator gas_ are described.[4] A workman who had entered a gasometer containing the gas died in ten minutes, and another remained unconscious for ten days and for another ten days suffered from mental disturbance, showing itself in hebetude and weakness of memory.

_Acetylene_ is poisonous to only a slight extent. Impurities in it, such as carbon bisulphide, carbonic oxide (present to the extent of 1-2 per cent.), and especially phosphoretted hydrogen gas, must be borne in mind.

American calcium carbide[5] yields acetylene containing 0·04 per cent. of phosphoretted hydrogen; Lunge and Cederkreutz have found as much as 0·06 per cent. in acetylene.

AMMONIA AND AMMONIUM COMPOUNDS

PREPARATION.—Ammonia and ammonium salts are now exclusively obtained as a bye-product in the dry distillation of coal, from the ammonia water in gas works, and as a bye-product from coke ovens.

The ammonia water of gas works contains from 2-3 per cent. of ammonia, some of which can be recovered on boiling, but some is in a non-volatile form, and to be recovered the compound must be decomposed. The volatile compounds are principally ammonium carbonate and, to a less extent, ammonium sulphide and cyanide; the non-volatile compounds are ammonium sulphocyanide, ammonium chloride, sulphate, thiosulphate, &c. Other noteworthy substances in ammonia water are pyridine, pyrrol, phenols, hydrocarbons, and tarry compounds.

Decomposition of the non-volatile compounds is effected by lime. Hence the ammonia water is distilled first alone, and then with lime. The distillate is passed into sulphuric acid, ammonium sulphate being formed. Distillation apparatus constructed on the principle usual in rectifying spirit is used, so that continuous action is secured; the ammonia water flows into the apparatus continuously and is freed of the volatile compounds by the steam. At a later stage milk of lime is added, which liberates the ammonia from the nonvolatile compounds.

Of the ammonium salts there require mention:

_Ammonium sulphate_ ((NH₄)₂SO₄), which serves for the production of other ammonium salts. It is usually centrifugalised out from the sulphuric acid tank previously described.

_Ammonium chloride_ (sal-ammoniac, NH₄Cl) is formed by bringing the ammonia fumes given off in the process described in contact with hydrochloric acid vapour. The crude salt so obtained is recrystallised or sublimed.

_Ammonium phosphate_ ((NH₄)₂HPO₄) is made in an analogous manner by leading ammonia into phosphoric acid. It is useful as an artificial manure.

_Ammonium carbonate_ is made either by bringing together ammonia vapour and carbonic acid or by subliming ammonium sulphate with calcium carbonate. It is very volatile. The thick vapour is collected and purified in leaden chambers.

A, B, C Columns; D Saturator; (a) Settling tank and regulator for flow of ammonia; (b) Economiser; (f) Milk of lime; (g) Pump]

_Caustic ammonia_ is prepared either from gas liquor or, more usually, from ammonium sulphate by distillation with caustic alkali in a continuous apparatus.

USE OF AMMONIA.—Ammonia is used in laundries and bleaching works in dyeing and wool washing. It is used especially in making ammonium salts, in the preparation of soda by the Solvay process (see Soda Manufacture), and in making ice artificially.

It is used also in the preparation of indigo, in lacquers and colours, and the extraction of chloride of silver, &c.

EFFECTS ON HEALTH.—Industrial ammonia poisoning is rare. It occurs most frequently in gas works and occasionally in its use, especially the manufacture of ammonium salts. Those engaged in subliming ammonium carbonate incur special risk, but often it is not the ammonia vapour so much as the escaping evil-smelling gases containing carbon bisulphide and cyanogen compounds which are the source of trouble.

Occasionally in the production of ice through leakage or by the breaking of carboys of ammonia accidental poisoning has occurred.

Some cases are cited from recent literature:

A worker was rendered unconscious and drowned in an ammonia water well.[1] Two workers were poisoned (one fatally) in the concentration of gas liquor. Three workers were gassed (one fatally) in the preparation of ammonium sulphate in a gas works. Probably as the result of excessive steam pressure gas water was driven over with the ammonia into the sulphuric acid vessel.[2]

Eulenberg[3] reports the occurrence of sulphuretted hydrogen gas poisoning in the production of ammonium salts. The workers succumbed as though shot, although work was being carried on in the open air. They recovered when removed from the poisonous atmosphere.

In a large room of a chemical factory phosphoric acid was being saturated with ammonia gas water in an iron lead-lined vessel. Carbonic acid gas and hydrogen gas were evolved, but not to such extent as to be noticeable in the large room. A worker not employed in the room had to do something close to the vessel, and inhaled some of the fumes given off. A few yards from the vessel he was found lying unconscious, and although removed into the open air failed to respond to the efforts at artificial respiration.[4]

Lewin, in an opinion delivered to the Imperial Insurance Office, describes poisoning in a man who during two days had been employed repairing two ammonia retorts in a chemical factory. On the evening of the second day he suffered from severe symptoms of catarrh, from which he died five days later. Lewin considered the case to be one of acute ammonia poisoning.[5]

Ammonia is frequently used in _fulling_ cloth, the fumes of which collect on the surface after addition of sulphuric acid to the settling vats. This is especially liable to occur on a Monday, owing to the standing of the factory over the Sunday, so that entrance into the vats without suitable precautions is strictly forbidden. Despite this, a worker did go in to fetch out something that had fallen in, becoming immediately unconscious. A rescuer succumbed also and lost his life. The first worker recovered, but was for long incapacitated by paralytic symptoms.

Cases of poisoning in _ice factories_ and refrigerator rooms from defective apparatus are reported.

Acute and chronic poisoning among sewer men are due mainly to sulphuretted hydrogen gas and only partly to ammonia. The more ammonia and the less sulphuretted hydrogen sewer gases contain the less poisonous are they.

CYANOGEN COMPOUNDS

TREATMENT OF THE MATERIALS USED IN GAS PURIFYING.—Cyanogen compounds are still sometimes prepared by the original method of heating to redness nitrogenous animal refuse (blood, leather, horn, hair, &c.) with potash and iron filings; potassium cyanide is formed from the nitrogen, carbon, and alkali, and this with the sulphur and iron present is easily converted into potassium ferrocyanide (yellow prussiate of potash, K₄FeC₆N₆) by lixiviation of the molten mass. It crystallises out on evaporation.

Cyanogen compounds are obtained in large quantity from the material used in purifying the gas in gas works. This saturated spent material contains, in addition to 30-40 per cent. of sulphur, 8-15 per cent. of cyanogen compounds and 1-4 per cent. of sulphocyanogen compounds.

By lixiviation with water the soluble ammonium salts are extracted from the purifying material. This solution furnishes _sulphocyanide of ammonium_, from which the remaining unimportant sulphocyanide compounds are obtained (used in cloth printing). The further treatment of the purifying material for potassium ferrocyanide is rendered difficult because of the sulphur, which is either removed by carbon bisulphide and the ferrocyanide obtained by treatment with quicklime and potassium chloride, or the mass is mixed with quicklime, steamed in closed vessels, lixiviated with water, and decomposed by potassium chloride; ferrocyanide of potassium and calcium separates out in crystals, and this, treated with potash, yields potassium ferrocyanide.

The well-known non-poisonous pigment Prussian blue is obtained by decomposing ferrocyanide of potash with chloride or oxide of iron in solution.

_Potassium cyanide_ (KCN) is prepared from potassium ferrocyanide by heating in absence of air, but it is difficult to separate it entirely from the mixture of iron and carbon which remains. All the cyanogen is more easily obtained in the form of potassium and sodium cyanide from potassium ferrocyanide by melting it with potash and adding metallic sodium.

The very poisonous _hydrocyanic acid_ (prussic acid, HCN) is formed by the action of acids on potassium or sodium cyanide; small quantities indeed come off on mere exposure of these substances to the air. The increasing demand for potassium cyanide has led to experimental processes for producing it synthetically.

One method consists in the production of potassium cyanide from potash and carbon in a current of ammonia gas. Small pieces of charcoal are freed from air, saturated with a solution of potash, dried in the absence of air, and heated in upright iron cylinders to 100° C., while a stream of ammonia gas is passed through.

Again, sodium cyanide is prepared from ammonia, sodium, and carbon by introducing a definite amount of sodium and coal dust into melted sodium cyanide and passing ammonia through. The solution is then concentrated in vacuo and sodium cyanide crystallises out on cooling.

USE OF CYANIDES.—Potassium cyanide is principally used in the recovery of gold, in gold and silver electroplating, in photography, for soldering (it reduces oxides and makes metallic surfaces clean), for the production of other cyanogen compounds, for the removal of silver nitrate stains, &c. Hydrocyanic acid gas is given off in electroplating, photography, in smelting fumes, in tanning (removing hair by gas lime), &c.

EFFECTS ON HEALTH.—Industrial cyanogen poisoning is rare. Weyl[1] states that he could find no case in any of the German factory inspectors’ reports for the twenty years prior to 1897, nor in some twenty-five volumes of foreign factory inspectors’ reports. I have found practically the same in my search through the modern literature.

Of the very few references to the subject I quote the most important.

A case of (presumably) chronic hydrocyanic acid poisoning is described in a worker engaged for thirteen years in silver electroplating of copper plates.[2] The plates were dipped in a silver cyanide solution and then brushed. After two years he began to show signs of vomiting, nausea, palpitation, and fatigue, which progressed and led to his death.

A case of sudden death is described[3] occurring to a worker in a sodium cyanide factory who inhaled air mixed with hydrocyanic acid gas from a leaky pipe situated in a cellar. The factory made sodium cyanide and ammonium sulphate from the residue after removal of the sugar from molasses. This is the only definite case of acute cyanogen poisoning in a factory known to me. I believe that under modern conditions, in which the whole process is carried on under negative pressure, chance of escape of cyanogen gases is practically excluded.

It should be mentioned that hydrocyanic acid vapour is given off in the burning of celluloid. In this way eight persons were killed at a fire in a celluloid factory.[4]

Skin affections are said to be caused by contact with fluids containing cyanogen compounds, especially in electroplating. It is stated that workers coming into contact with solutions containing cyanides may absorb amounts sufficient to cause symptoms, especially if the skin has abrasions. Such cases are described.[5] In electroplating, further, in consequence of the strong soda solutions used, deep ulceration and fissures of the skin of the hand can be caused.

COAL TAR AND TAR PRODUCTS

Of the products of the illuminating gas industry tar has considerably the most importance. Coal tar as such has varied use in industry, but far greater use is made of the products obtained by fractional distillation from it such as benzene, toluene, naphthalene, anthracene, carbolic acid, pyridine, and the other constituents of tar, a number of which form the starting-point in the production of the enormous coal-tar dye industry. Especially increasing is the consumption of benzene. In Germany alone this has increased in ten years from 20 to 70 million kilos. This is partly due to the need of finding some cheap substitute for benzine, the consumption and cost of which has increased, and it has in many respects been found in benzene.

Besides benzene and its homologues, toluene, anthracene, and naphthalene are valuable. Anthracene is used in the manufacture of alizarine and naphthalene in that of artificial indigo and of the azo-colours. Carbolic acid (phenol) and the homologous cresols serve not only as disinfectants but also in the manufacture of numerous colours and in the preparation of picric acid and salicylic acid. Further, a number of pharmaceutical preparations and saccharin are made from the constituents of tar.

The important _constituents of tar_ are:

1. Hydrocarbons of the methane series: paraffins, olefines; hydrocarbons of the aromatic series: benzene and its homologues, naphthalene, anthracene, phenanthrene, &c.

2. Phenols (cresols, naphthols).

3. Sulphides: sulphuretted hydrogen, carbon bisulphide, mercaptan, thiophene.

4. Nitrogen compounds: ammonia, methylamine, aniline, pyridine, &c.

5. Fifty to sixty per cent. of tar consists of pitch constituting a mixture of many different substances which cannot be distilled without decomposition.

_Crude tar_, i.e. tar which separates in the dry distillation of coal, is employed as such for preserving all kinds of building materials, for tarring streets, as plastic cement, as a disinfectant, in the preparation of roofing paper or felt, lampblack, briquettes, &c.

_Brattice cloth_ and _roofing felt_ are made by passing the materials through hot tar and incorporating sand with them; in doing this heavy fumes are given off.

_Lampblack_ is made by the imperfect combustion of tar or tar oil by letting them drop on to heated iron plates with as limited an air supply as possible; the burnt gases laden with carbon particles are drawn through several chambers or sacks in which the soot collects.

_Briquettes_ (patent fuel) are made by mixing small coal (coal dust) with tar or pitch and then pressing them in moulds.

The separation and recovery of the valuable ingredients is effected by _fractional distillation_. This is carried out by heating the tar at gradually increasing temperature in a wrought-iron still, the bottom of which is arched and having a cast-iron still head, or in horizontal boilers by direct fire. Before commencing the distillation the tar is freed as far as possible of water by storage. On gradual increase of temperature the volatile constituents, the so-called ‘light oil,’ and later the heavier volatile constituents come over. The constituents are liberated in a gaseous state and are collected in fractions. The pitch remains behind in the still. Considerable quantities of coal tar are not distilled for pitch. Often the light oils and a portion of the heavy oils are collected, when soft pitch remains, or, if the light oils and only a very small portion of the heavy oils are collected, _asphalt_ remains behind, this residue being used as a basis for the manufacture of roofing felt. The vapours are condensed in iron coils round which cold water circulates. The receivers in which the distillate is caught are changed at definite times as the temperature gradually rises. If five fractions have come over they are called (1) first runnings, (2) light oil to 170° C., (3) middle oil (carbolic oil to 230° C.), (4) heavy oil to 270° C., and lastly (5) anthracene oil, which distills at over 270° C.; the pitch remaining behind is let out of the still by an opening at the bottom.

We will briefly sketch the further treatment and use of these fractions, so far as a knowledge of the most important processes is necessary for our purpose.

1. The _light oils_ (including first runnings) coming over up to 170° C. are again distilled and then purified with sulphuric acid in lead-lined cast-iron or lead-lined wooden tanks. The dark-coloured acid used for purifying after dilution with water, which precipitates tarry matters, is treated for ammonium sulphate; the basic constituents of the light oils extracted with sulphuric acid and again liberated by lime yield _pyridine_ (C₅H₅N) and the homologous pyridine bases, a mixture of which is used for denaturing spirit. After the light oils have been washed with dilute caustic soda liquor, whereby the phenols are removed, they are separated by another fractional distillation into (_a_) crude benzol (70°-130° C.) and (_b_) solvent naphtha (boiling-point 130°-170° C.).

_Crude benzol_ (70°-140° C.) consists chiefly of benzene and toluene and is separated into its several constituents in special rectifying apparatus. For this production of pure benzene (boiling-point 80°-82° C.) and pure toluene (boiling-point 110° C.) fractionating apparatus is used (fig. 24).

The _commercial products_ in use which are obtained from the fractional distillation of the light oil are:

(_a_) _Ninety per cent. benzol_, so called because in the distillation 90 per cent, should come over at a temperature of 100° C. It is made up of 80-85 per cent. benzene, 13-15 per cent. toluene, 2-3 per cent. xylene, and contains, as impurities, traces of olefines, paraffins, sulphuretted hydrogen, and other bodies.

(_b_) _Fifty per cent. benzol_ contains 50 per cent. of constituents distilling at 100° C. and 90 per cent. at 120° C.; it is a very mixed product, with only 40-50 per cent. of benzene.

(_c_) _Solvent naphtha_, so called because it is largely used for dissolving rubber, is free from benzene, but contains xylene and its homologues and other unknown hydrocarbons.

A Still body; B Analysing column; C Cooler; D Condenser for pure distillate.]

Benzol is widely used. Ninety per cent. benzol is largely used in the chemical industry, serving for the preparation of dye stuffs, pharmaceutical preparations, scents, &c. In other industries it took the place of benzine and also of turpentine oil, especially in the paint industry, since it evaporates quickly and readily dissolves resins. Hence it is used in the preparation of quick drying ship’s paints, as a protection against rust, and as an isolating lacquer (acid proof colours) for electrical apparatus, in the production of deck varnishes, and as a solvent of resins.

This use of benzol in the paint industry is by no means unattended with danger, as benzol is poisonous. Far less harmful, if not altogether without risk, is use of benzol free solvent naphtha—but this evaporates only slowly and hence cannot take the place of benzol.

Benzol serves further for fat extraction from bones in manure factories and of caffein from coffee beans.

Again, it is used as a motive power in motor vehicles.

The solvent naphtha above mentioned with boiling-point above 140° C. and all the light oils are employed in chemical cleaning and for dissolving indiarubber (see Indiarubber).

These are known in the trade erroneously as ‘benzine,’ which unfortunately often leads to confusion with petroleum benzine (see Petroleum) and to mistakes in toxicological accounts of poisoning.

2. Between 150° and 200° C. the _middle oil_ comes over, from which on cooling _naphthalene_ (C₁₀H₈) crystallises out, and is subsequently washed with caustic soda liquor and with acid; it is re-distilled and hot pressed. The remaining liquor yields, when extracted with caustic soda, _phenol_ (carbolic acid, C₆H₅OH), which, on addition of sulphuric acid or carbonic acid, separates from the solution and then—generally in special factories—is obtained pure by distillation and special purifying processes.

From the sodium salt of carbolic acid (sodium phenolate) _salicylic acid_ (C₆H₄OH.COOH) is obtained by combination with compressed CO₂ at a temperature of 150° C. _Picric acid_ (trinitrophenol, C₆H₂OH.(NO₂)₃) is obtained by treating phenol with a mixture of sulphuric and nitric acids (nitration). The yellow crystals of this explosive which separate are carefully washed, recrystallised, centrifugalised, and dried.

3. The _heavy oils_ which come over between 200° and 300° C. containing cresols, naphthols, naphthaline, quinoline bases, fluid paraffins, &c., are seldom separated further. The disinfectants lysol, sapocarbolic, &c., are obtained from such fractions.

The heavy oils are much in use for _impregnating wood_ (piles, railway sleepers, &c.), to prevent rotting. This is done in special creosoting installations. The wood is first freed from moisture under vacuum and lastly the heavy oil forced in. This is a better means of preserving timber than the analogous method by means of chloride of zinc.

4. _Anthracene oil_ or ‘green oil’ comes over between 300° and 400° C. and contains the valuable anthracene which crystallises out, is separated from the oil in filter presses, or dried in centrifugal machines. _Alizarin_ dyes are made from it. Raw anthracene oil further is used commercially as a paint under the name of carbolineum for preserving wood.

5. The _pitch_ remaining behind in the still serves (like tar) for making varnishes, patent fuel, &c. For our purpose use of pitch in the preparation of iron varnishes which adhere to metals and protect them from oxidation have interest. Pitch and the heavy oils are melted together or, if for thin varnishes, dissolved in solvent naphtha. The volatile constituents evaporate after the coat has been applied.

EFFECTS ON HEALTH.—Severe injury to health or poisoning cases scarcely arise through manipulations with or use of tar. Inhalation, however, of large quantities of tar vapour is without doubt unpleasant, as a number of poisonous substances are contained in the fumes. And the ammonia water which separates on standing can give off unpleasantly smelling odours from the sulphur compounds in it, especially if it comes into contact with waste acids, with consequent development of sulphuretted hydrogen gas.

I could not find in the literature of the subject references to any clearly proved case of poisoning from tar emanations. But deserving of mention in this connection are the _effects on the skin_ caused by tar.

Workers coming into contact with tar suffer from an inflammatory affection of the skin, so-called tar eczema, which occasionally takes on a cancerous (epithelioma) nature similar to chimney-sweep’s cancer, having its seat predominantly on the scrotum. In lampblack workers who tread down the soot in receptacles the malady has been observed to affect the lower extremities and especially the toes.

In tar distillation and in the _production_ and _use_ of _benzene_ industrial poisoning frequently occurs. Many cases are recorded, but in several the immediate exciting cause is doubtful, and consequently it is often difficult to classify the cases.

Most frequently the manufacture and use of benzene come in question. Besides this, in tar distillation poisoning may be caused by other substances, such as sulphuretted hydrogen gas, carbonic oxide gas, &c. In the production of antipyrin, aspirin, &c., and in the preparation and use of anthracene injury to health is recognised.

From the list of recognised cases of these forms of poisoning the most characteristic are chosen from the recent literature on the subject.

The Prussian factory inspectors’ reports for 1904 describe the following: In cleaning out a tar still two workers were killed by inhalation of gas. The nature of the gas was not ascertained. But what probably happened was that the cock on the foul gas pipe collecting the gases from the stills leaked and allowed fumes to pass over from one still to another.

A foreman and worker were rendered unconscious on entering a receiver for heavy oil for cleaning purposes. On treatment with oxygen gas they speedily recovered.

_Industrial benzene poisoning_ is especially frequent now in view of the increasing use to which it is put. Several cases have proved fatal.

A worker, for instance, forgot to open the cock for the water to cool the condenser, so that some of the benzene vapour remained uncondensed. The case proved fatal.

The Report of the Union of Chemical Industry for 1905 stated that a worker on night duty, whose duty it was to regulate the introduction of steam and the cooling of the benzol plant, was found lying dead in front of the building. Inquiry showed that he had not opened the valve for running the distillate into the appropriate receiver. Eight thousand litres overflowed.

In an indiarubber extracting factory a worker was rendered unconscious while inspecting a benzol still; before entering he had omitted to observe the instructions to drive steam through and have a mate on watch at the manhole. Two other workmen were similarly affected who went to the rescue without adoption of precautions. Only one survived.

In a further accident (already mentioned under ‘Coke Furnaces’) two workmen were killed. In the factory in question the thick tar from the coke ovens was being distilled under slight pressure. The air pumps, however, were out of order, and temporary use was being made of Körting’s injectors, whereby the steam and tar constituents were cooled and led into the drain in front of the closet, near to which was a ventilating shaft. Probably, in addition to benzene and its homologues, sulphuretted hydrogen and cyanogen compounds were present in the poisonous gases.

In cleaning out a benzene extracting apparatus a workman was killed by the stagnant fumes in it.

A similar case of benzene poisoning occurred in a naphthalamine works through inspecting an extracting vessel which had contained benzene and naphthalamine and had to be cleaned. The vessel had been empty for twenty-two hours and had been washed and ventilated, but through a leaking pipe benzene had dropped down into it. The workman engaged was rendered unconscious inside the retort, but was rescued by an engineer equipped with a breathing helmet. Others who without such apparatus tried to effect a rescue were overcome, and one who had entered the retort succumbed.[1]

Benzene poisoning has often occurred in the cleaning of tanks, &c., for the transport and storage of the substance. The following examples are taken from the Reports of the Union of Chemical Industry.

A worker during the pause for breakfast had, unknown to his employer, cleaned out an empty truck for crude benzol. Later he was with difficulty removed unconscious through the manhole and could not be resuscitated. Only a short time previously a similar occurrence had taken place in the same factory.

Two further fatal cases were reported in 1908 in the cleaning out of railway tank waggons. The tank had previously been thoroughly sprayed with water. The partition plates which are required in such tanks increase the difficulty of cleaning from the manhole. After the foreman had tested the air by putting his head inside and considered it free from danger, a man entered to clean out the deposit; another man on watch outside had evidently gone in for rescue purposes. Resuscitation in both cases failed.

A worker died and several were affected in the cleaning out of a benzol storage tank in a tar distillery. The tank had had air blown through it several weeks before, and had been thoroughly cleaned by steam and water. Also in the inspection the greatest care was taken in only permitting work for short spells. This shows that, notwithstanding great care, the last traces of benzol cannot be entirely removed and that quite small quantities are sufficient to cause severe and even fatal poisoning. Workers should only clean out tanks, therefore, when properly equipped with helmets.

In the German factory inspectors’ reports for 1902 a case of intoxication is described in a man who was engaged painting the inside of an iron reservoir with an asphalt paint dissolved in benzol.

Of special interest is a fatal case from inhalation of benzol fumes in a rubber factory. Rubber dissolved in benzol was being rubbed into the cloth on a spreading machine in the usual way. The cloth then passes under the cleaning doctor along the long heated plate to the end rolls. Of the three men employed at the process one was found to be unconscious and could not be brought round again.

The cases described[2] of poisoning with impure benzol in a pneumatic tyre factory in Upsala are, perhaps, analogous. Here nine young women had severe symptoms, four of whom died.

In reference to the cases which occurred in rubber factories it is conceivable that carbon bisulphide played a part, since in such factories not only are mixtures of benzol and carbon bisulphide used, but also frequently the ‘first runnings’ of benzol, which, on account of the high proportion (sometimes 50 per cent.) of carbon bisulphide in them, make an excellent solvent for rubber.

From some coke ovens crude benzol was collected in two large iron receivers. They were sunk in a pit projecting very little above the ground. To control the valves the workmen had to mount on the receiver, the manholes of which were kept open during filling. The pit was roofed over and two wooden shafts served both for ventilation and as approaches to the valves. One summer day benzol had been blown in the usual way into a railway truck and a worker had entered the space to control the valves. Some time afterwards he was found in a doubled-up position on the receiver, grasping the valves, from which later he fell off down to the bottom of the pit. Three rescuers entered, but had to retire as they became affected. A fourth worker, in the presence of the manager, was let down by a rope, but succumbed immediately and was dragged up a corpse. Finally, equipped with a smoke helmet, a rescuer brought up the lifeless body of the first man. It was believed that the benzol had distilled over warm and had evaporated to such an extent as to fill with fumes the unsuitably arranged and inadequately ventilated space. Possibly other volatile compounds were responsible for the poisoning.[3]

A similar though less serious accident occurred to a foreman who forgot to set the cooling apparatus at work at the commencement of distillation, and became unconscious from the escaping fumes, as also did a rescuer. The latter was brought round by oxygen inhalation, but the former, although alive when recovered, succumbed despite efforts at artificial respiration.

A fatal case occurred in an aniline factory where benzol fumes had escaped owing to faulty arrangement of the valves. The worker, although ordered at once to leave the room, was found there ten minutes later dead.

Interesting are the following cases of accidents due to use of paints containing benzol.

In painting a retort with an anti-corrosive paint called ‘Original Anti-corrosive,’ unconsciousness followed on completion of the painting, but by prompt rescue and medical assistance life was saved. The accident was attributed to benzol fumes from the paint insufficiently diluted by the air coming in at the open manhole. A similar case arose from use of a rust-preventing paint—‘Preolith’—and only with difficulty was the man using it pulled out from the inside of the steam boiler. Although resuscitated by oxygen inhalation, he was incapacitated for eight days. Crude benzol was a constituent of ‘Preolith.’ Obviously use of such paints in closely confined spaces is very risky.

The frequency of such poisonings caused Schaefer,[4] Inspector of Factories in Hamburg, to go fully into the question. He lays stress on the dangerous nature of paints containing a high proportion of benzol, but considers use of unpurified constituents with boiling-point between 130°-170° C., such as solvent naphtha, as free from risk (cf. in Part II the experiments on benzene and the commercial kinds of benzol). Schaefer mentions that in 1903 and 1904 cases of unconsciousness from painting the inside of boilers were numerous. The proportion of benzol in the paints was 20-30 per cent. In 1905 and 1906 the cases were attributable rather to inhalation of hydrocarbons in cleaning of apparatus. Use of ‘Dermatin’ affected two painters. One case in 1906 happened to a man painting the double bottom of a ship in Hamburg harbour with ‘Black Varnish Oil’ through the manhole, in doing which he inhaled much of the fumes. This paint consisted of coal-tar pitch in light coal-tar oil, the latter constituent (distilling at 170° C.) amounting to 31-33 per cent. Investigation showed further that the bulk of the tar oil volatilised at ordinary temperatures and so quickly dried. Sulphuretted hydrogen gas was given off on slight warming. The person after using it for some time felt poorly, and then became ill with severe inflammation of the respiratory passages, which proved fatal after twenty-four days.

Several similar cases occurred in 1908 and 1909. Painting the inside of a boiler with ‘Auxulin’ caused unconsciousness in four persons, of whom three were rescuers. A fatal case was due to use of a patent colour containing 30-40 per cent. benzol in an entirely closed-in space (chain-well), although the worker was allowed out into fresh air at frequent intervals.

A case of chronic industrial xylene poisoning is described in a worker using it for impregnating indiarubber goods. The symptoms were nervous, resembling neurasthenia.

Some of the cases of poisoning, especially when severe and fatal, in the production of distillation constituents of coal tar are doubtless attributable to _sulphuretted hydrogen gas_. Thus in England, in the years 1901-3, there were eleven fatal and as many other severe cases reported from tar distilleries, of which the majority were due to sulphuretted hydrogen gas.

One case of _carbonic oxide_ poisoning in coal-tar distillation is described.[5] In cleaning out pitch from a still fourteen days after the last distillation a workman succumbed to carbonic oxide poisoning. This is at all events a rare eventuality, since no other case is to be found in the literature of the subject, but it is a proof that in the last stage of coal-tar distillation carbonic oxide plays a part.

Mention must be made of the frequent occurrence of severe skin affections in _anthracene workers_; they take the form of an eruption on the hands, arms, feet, knees, &c., and sometimes develop into cancer.

Observations in a chemical factory since 1892 showed that of thirty thus affected in the course of ten years twenty-two came into contact with paraffin.

Artificial Organic Dye Stuffs (Coal-tar Colours)

MANUFACTURE.—The starting-points for the preparation of artificial coal-tar dyes are mainly those aromatic compounds (hydrocarbons) described in the preceding section. Besides these, however, there are the derivatives of the fatty series such as methyl alcohol (wood spirit), ethyl alcohol, phosgene, and, latterly, formaldehyde.

The _hydrocarbons of the benzene series_ from tar distillation are delivered almost pure to the colour factory. Of these benzene, toluene, xylene, naphthalene, anthracene, and the phenols, cresols, &c., have to be considered.

Further treatment is as follows:

1. Nitration, i.e. introduction of a nitro-group by means of nitric acid.

2. Reduction of the nitrated products to amines.

3. Sulphonation, i.e. conversion to sulphonic acids by means of concentrated sulphuric acid.

4. The sulphonic acids are converted into phenols by fusing with caustic soda.

5. Introduction of chlorine and bromine.

_Nitro-derivatives_ are technically obtained by the action of a mixture of nitric and concentrated sulphuric acids on the aromatic body in question. The most important example is _nitrobenzene_.

Benzene is treated for several hours in cylindrical cast-iron pans with nitric and concentrated sulphuric acids. The vessel is cooled externally and well agitated. A temperature of 25° C. should not be exceeded.

On standing the fluid separates into two layers: the lower consists of dilute sulphuric acid in which there is still some nitric acid, and the upper of nitrobenzene. The latter is freed of remains of acid by washing and of water by distillation. _Toluene_ and _xylene_ are nitrated in the same way. _Dinitro products_ (such as metadinitrobenzene) are obtained by further action of the nitro-sulphuric acid mixture on the mononitro-compound at higher temperature.

For conversion of phenol into _picric acid_ (trinitrophenol) the use of a nitro-sulphuric acid mixture is necessary.

The _aromatic bases_ (aniline, toluidine, xylidine) are obtained by reduction of the corresponding nitro-compound by means of iron filings and acid (hydrochloric, sulphuric, or acetic). Thus in the case of _aniline_ pure nitrobenzene is decomposed in an iron cylindrical apparatus, provided with agitators and a condenser, and avoidance of a too violent reaction, by means of fine iron filings and about 5 per cent. hydrochloric acid. After completion of the reaction the contents are rendered alkaline by addition of lime and the aniline distilled over. Manufacture of _toluidine_ and _xylidine_ is analogous.

_Dimethylaniline_ is obtained by heating aniline, aniline hydrochloride, and methyl alcohol.

_Diethylaniline_ is prepared in an analogous way with the use of ethyl alcohol.

By the action of nitrous acid (sodium nitrite and hydrochloric acid) on the acid solution of the last-named compound the _nitroso compounds_ are formed.

_Sulphonic acids_ arise by the action of concentrated or fuming sulphuric acid on the corresponding bodies of the aromatic series: benzene disulphonic acid from benzene and fuming sulphuric acid, &c.

_Phenols_ and _cresols_ are obtained pure from tar distillation. The remaining hydroxyl derivatives (resorcin, α- and β-naphthol, &c.), are generally obtained by the action of concentrated caustic soda on aromatic sulphonic acids.

The most important aromatic aldehyde, _benzaldehyde_, is obtained from toluene; on introducing chlorine at boiling temperature benzyl chloride is first formed, then benzal-chloride and finally benzo-trichloride. In heating benzal-chloride with milk of lime (under pressure) benzaldehyde is formed (C₆H₅COH).

_Picric acid_ and _naphthol yellow_ belong to the _nitro dyestuffs_; the last named is obtained by sulphonating α-naphthol with fuming sulphuric acid and by the action of nitric acid on the sulphonated mixture.

Nitroso derivatives of aromatic phenols yield (with metal oxides) the material for production of nitroso dyestuffs. To these belong naphthol green, &c.

The most important _azo dyestuffs_ technically are produced in principle by the action of nitrous acid on the aromatic amines. The amido compound is converted into the diazo salt by treatment with sodium nitrite in acid solution. Thus diazo-benzene is made from aniline. Diazo compounds are not usually isolated but immediately coupled with other suitable compounds—amido derivatives, phenols—i.e. converted into azo compounds.

I Nitric acid
II Balance
III Storage tank
IV Nitrating pan
V Waste acid tank
VI Acid egg
VII Hydrocarbon
VIII Balance
IX Storage tank
X Washing vessel
XI Centrifugal machine
XII Egg
- - - Exhaust ventilation pipe.]

The combination of the two constituents takes place at once and quantitatively. The colour is separated from the aqueous solution by salting-out, and is then put through a filter press. The reactions are carried out generally in wooden vats arranged in stages. Besides a second, a third constituent can be introduced, and in this way naphthol—and naphthylamine sulphonic acids yield a large number of colouring matters. A very large number of azo dyestuffs can thus be produced by the variation of the first component (the primary base) with the second and again with the third component, but it would carry us too far to deal further with their preparation.

_Anthracene colours_—yielding so-called direct dyes—are prepared from anthracene, which is converted into anthraquinone by the action of bichromate and dilute sulphuric acid when heated; the crude ‘quinone’ is purified with concentrated sulphuric acid and converted into anthraquinone monosulphonic acid to serve in the preparation of _alizarin_, which is made from it by heating for several days with concentrated caustic soda to which sodium chlorate is added. The process is carried on in cast-iron pans provided with agitators.

_Alizarin_ is the starting-point for the alizarin dyes, but of their production we will not speak further, as they, and indeed most of the coal-tar dyes, are non-poisonous.

_Indigo_ to-day is generally obtained by synthesis. It is prepared from phenylglycine or phenylglycine ortho-carboxylic acid, which on heating with sodamide becomes converted into indoxyl or indoxyl carboxylic acid. These in presence of an alkali in watery solution and exposure to the oxygen of the air immediately form indigo. The necessary glycine derivatives are obtained by the action of monochloracetic acid on aniline or anthranilic acid, which again are derived from naphthalene (by oxidation to phthalic acid and treatment of phthalimide with bleaching powder and soda liquor).

_Fuchsin_ belongs to the group of triphenylmethane dyestuffs, with the production of which the epoch of coal-tar colour manufacture began, from the observation that impure aniline on oxidation gave a red colour. The original method of manufacture with arsenic acid is practically given up in consequence of the unpleasant effects which use and recovery of large quantities of arsenic acid gave rise to. The method consisted in heating a mixture of aniline and toluidine with a solution of arsenic acid under agitation in cast-iron cylinders. The cooled and solidified mass from the retorts was boiled, and from the hot solution, after filtration, the raw fuchsin was precipitated with salt and purified by crystallisation.

Now by the usual nitrobenzene process, aniline, toluidine, nitrobenzene, and nitrotoluene are heated with admixture of hydrochloric acid and some iron protochloride or zinc chloride. Further treatment resembles the arsenic process.

By alkylation, i.e. substitution of several hydrogen atoms of the amido-groups by ethyl, &c., through the action of alkyl halogens and others, it was found possible to convert fuchsin into other triphenylmethane colours. But it was soon found simpler to transfer already alkylated amines into the colours in question. Thus, for example, to prepare _methyl violet_ dimethyl aniline was heated for a long time with salt, copper chloride, and phenol containing cresol in iron mixing drums. The product is freed from salt and phenol by water and calcium hydrate, subsequently treated with sulphuretted hydrogen or sodium sulphide, and the colour separated from copper sulphide by dissolving in dilute acid.

Mention must be made, finally, of the _sulphur dyes_ obtained by heating organic compounds with sulphur or sodium sulphide. For the purpose derivatives of diphenylamine, nitro- and amido-phenols, &c., serve as the starting-point.

EFFECTS ON HEALTH.—From what has been said of the manufacture of coal-tar dyes it is evident that poisoning can arise from the initial substances used (benzene, toluene, &c.), from the elements or compounds employed in carrying out the reactions (such as chlorine, nitric acid, sulphuric acid, arsenious acid, sodium sulphide, and sulphuretted hydrogen gas), from the intermediate bodies formed (nitro and amido compounds, such as nitrobenzene, dinitrobenzene, aniline, &c.), and that, finally, the end products (the dyes themselves) can act as poisons. It has already been said that most of the dyes are quite harmless unless contaminated with the poisonous substances used in their manufacture.

We have seen that many of the raw substances used in the manufacture of coal-tar dyes are poisonous, and we shall learn that several of the intermediate products (especially the nitro and amido compounds) are so also.

According to Grandhomme,[1] of the raw materials benzene is the one responsible for most poisoning. He describes two fatal cases of benzene poisoning. In one case the worker was employed for a short time in a room charged with benzene fumes, dashed suddenly out of it, and died shortly after. In the other, the workman was employed cleaning out a vessel in which lixiviation with benzene had taken place. Although the vessel had been steamed and properly cooled, so much benzene fume came off in emptying the residue as to overcome the workman and cause death in a short time.

Grandhomme describes no injurious effect from naphthalene nor, indeed, from anthracene, which he considered was without effect on the workers.

Similarly, his report as to nitrobenzene was favourable. No reported case of poisoning occurred among twenty-one men employed, in some of whom duration of employment was from ten to twenty years. Aniline poisoning, however, was frequent among them. In the three years there was a total of forty-two cases of anilism, involving 193 sick days—an average of fourteen cases a year and sixty-four sick days. None was fatal and some were quite transient attacks.

In the fuchsin department no cases occurred, and any evil effects in the manufacture were attributable to arsenic in the now obsolete arsenic process. Nor was poisoning observed in the preparation of the dyes in the remaining departments—blues, dahlias, greens, resorcin, or eosin. In the manufacture of methylene blue Grandhomme points out the possibility of evolution of arseniuretted hydrogen gas from use of hydrochloric acid and zinc containing arsenic. Poisoning was absent also in the departments where alizarine colours and pharmaceutical preparations were made.

Among the 2500-2700 workers Grandhomme records 122 cases of industrial sickness in the three years 1893-5, involving 724 sick days. In addition to forty-two cases of anilism there were seventy-six cases of lead poisoning with 533 sick days. Most of these were not lead burners, but workers newly employed in the nitrating department who neglected the prescribed precautionary measures. Lastly, he mentions the occurrence of chrome ulceration.

The frequency of sickness in the Höchst factory in each of the years 1893-5 was remarkably high: 126 per cent., 91 per cent., and 95 per cent. Much less was the morbidity in the years 1899-1906—about 66 per cent.—recorded by Leymann[2]—probably the same Höchst factory with 2000 to 2200 employed. And the cases of industrial poisoning also were less. He cites only twenty-one in the whole of the period 1899-1906. Of these twelve were due to aniline, involving thirty sick days, only five to lead poisoning, with fifty-four sick days, one to chrome ulceration, one to arseniuretted hydrogen gas (nine sick days), and one fatal case each from sulphuretted hydrogen gas and from dimethyl sulphate. In 1899, of three slight cases of aniline poisoning one was attributable to paranitraniline (inhalation of dust), and the two others to spurting of aniline oil on to the clothing, which was not at once changed. Of the four cases in 1900, one was a plumber repairing pipes conveying aniline and the others persons whose clothes had been splashed.

In 1903 a worker employed for eleven and a half years in the aniline department died of cancer of the bladder. Such cancerous tumours have for some years been not infrequently observed in aniline workers, and operations for their removal performed. Leymann thinks it very probable that the affection is set up, or its origin favoured, by aniline. This view must be accepted, and the disease regarded as of industrial origin. Three slight cases in 1904 and 1905 were due partly to contamination of clothing and partly to inhalation of fumes. Of the five cases of lead poisoning three were referable to previous lead employment. Perforation of the septum of the nose by bichromate dust was reported once only. A fatal case from sulphuretted hydrogen gas and a case of poisoning by arseniuretted hydrogen gas occurred in 1906, but their origin could not be traced.

In large modern aniline dye factories, therefore, the health of the workers is, on the whole, good and industrial poisoning rare. Comparison of the two sets of statistics show that improvement in health has followed on improved methods of manufacture. Such cases of aniline poisoning as are reported are usually slight, and often accounted for by carelessness on the part of the workers.

Data as to the health of workers in factories manufacturing or using nitro compounds are given in the English factory inspectors’ reports for 1905. Even with fortnightly medical examination in them, more than half the workers showed signs of anæmia and slight cyanosis. Two men in a factory employing twelve men in the manufacture of nitro compounds were treated in hospital for cyanosis, distress of breathing, and general weakness. One had only worked in the factory for nine days. In another badly ventilated factory, of twenty persons examined fourteen showed bluish-grey coloration of the lips and face, ten were distinctly anæmic, and six showed tremor and weakness of grasp.

Nitrobenzene poisoning arises from the fumes present in aniline and roburite factories. Acute and chronic poisoning by nitro compounds of the benzene series are described, brought about by accident (fracture of transport vessels) and by carelessness (splashing on to clothes). Cases of optic neuritis (inflammation of the optic nerve) as a result of chronic nitrobenzene poisoning are described.

Dinitrobenzene and other nitro and dinitro compounds are present in safety explosives. Thus roburite and bellite consist of metadinitrobenzene and ammonium nitrate; ammonite of nitronaphthalene and ammonium nitrate; securite of the materials in roburite with ammonium oxalate in addition. In roburite there may be also chlorinated nitro compounds.

Leymann,[3] describing accidents in the preparation of nitrophenol and nitrochloro compounds, mentions four fatal cases occurring in the manufacture of black dyes from mono- and di-nitrophenols as well as mono- and di-nitrochlorobenzene and toluene. In three of the cases dinitrophenol was the compound at fault owing to insufficient care in the preparation,—the result of ignorance until then of risk of poisoning from mono- and tri-nitrophenol. One of the men had had to empty a washing trough containing moist dinitrophenol. He suddenly became collapsed, with pain in the chest, vomiting, fever, and convulsions, and died within five hours. Another suffered from great difficulty of breathing, fever, rapid pulse, dilatation of the pupils, and died within a few hours in convulsions. Two further cases of nitrochlorobenzene poisoning are referred to, one of which was fatal. Four chlorobenzene workers after a bout of drinking were found unconscious in the street, and only recovered after eight to ten hours in hospital. The symptoms were grey-blue colour of the skin, pallor of mucous membranes, lips, nose, and conjunctivæ, and peculiar chocolate-coloured blood.

Many cases of poisoning from roburite are recorded.[4] In the Witten roburite factory it is stated that during the years 1890-7 almost all the workers had been ill.[5] Only three looked healthy—all the others suffered from more or less pallor, blue lips, and yellowish conjunctivæ.

A case of chlorobenzene poisoning was reported with symptoms of headache, cyanosis, fainting attacks, difficulty of breathing, &c., in a man who had worked only three weeks with the substance.[6]

In the nitrotoluene department of an explosives factory a number of the workmen suffered from symptoms of distress in breathing, headache, &c., of whom two, employed only a short time, died. The poisoning was attributed, partly to nitrotoluene and partly to nitrous fumes. As a contributing cause it was alleged that in view of shortage of hands unsuitable persons were engaged who neglected precautions.[7]