Chapter VIII: Part I (3)

It must be borne in mind that practically all chromium compounds are not alike poisonous. Chrome ironstone is non-poisonous, and the potassium and sodium salts are by far the most poisonous, while the neutral chromate salts and chromic oxide are only slightly so. Pander found that bichromates were 100 times as poisonous as the soluble chromium oxide compounds, and Kunkel is of opinion that poisonous effect shown by the oxides is attributable to traces of oxidation into chromic acid.

Lewin, on the other hand, declares in a cautionary notice for chrome workers generally that all chromium compounds are poisonous, and therefore all the dyes made from them.[2]

In the manufacture of bichromates, chance of injury to health arises partly from the dust, and partly from the steam, generated in pouring water over the molten mass. The steam carries particles of chromium compounds with it into the air. In evaporating the chromate solutions, preparation of the bichromate, breaking the crystals, drying and packing, the workers come into contact with the substance and the liquors. Chrome ulceration is, therefore, most frequently found among those employed in the crystal room and less among the furnace hands.

From 3·30 to 6·30 mg. of bichromate dust have been found in 1 c.m. of air at breathing level in the room where chromate was crushed, and 1·57 mg. where it was packed. Further, presence of chromium in the steam escaping from the hot chrome liquors has been proved.[3]

Poisoning from use of chrome colours is partly attributable to lead, as, for example, in making yellow coloured tape measures, yellow stamps, and from the use of coloured thread. Gazaneuve[4] found 10 per cent. of lead chromate in such thread, in wool 18 per cent., and in the dust of rooms where such yarn was worked up 44 per cent.

Use of chrome colours and mordants is accompanied by illness which certainly is referable to the poisonous nature of the chrome. In France use of chromic and phosphoric acid in etching zinc plates has caused severe ulceration.

Bichromate poisoning has been described among photographers in Edinburgh in the process of carbon printing, in which a bichromate developer is used.[5]

There is much evidence as to occurrence of skin eruptions and development of pustular eczema of the hands and forearms of workers in chrome tanneries.[6] In a large leather factory where 300 workers were constantly employed in chrome tanning nineteen cases of chrome ulceration were noted within a year. Injury to health was noted in a chrome tannery in the district of Treves, where the two bath process was used, from steam developed in dissolving the chromate in hot water.

Finally, I have found several records in 1907 and 1908 of perforation of the septum in Bohemian glass workers.

MANGANESE COMPOUNDS

The raw material of the manganese industry is _hausmannite_ (manganese dioxide, MnO₂). This is subjected to a crushing process, sorted, sieved, finely ground, washed, and dried. The pure finely ground manganese dioxide is much used in the chemical industry, especially in the recovery of chlorine in the Weldon process and in the production of _potassium permanganate_, which is obtained by melting manganese dioxide with caustic soda and potassium chlorate or nitre, lixiviation and introduction of carbonic acid, or better by treatment with ozone.

Manganese is also used in the production of colours: the natural and artificial umbers contain it; in glass works it is used to decolourise glass, and also in the production of coloured glass and glazes; in the manufacture of stove tiles, and in the production of driers for the varnish and oil industry. Manganese and compounds of manganese are dangerous when absorbed into the system as dust.

Already in 1837 nervous disorders had been described in workmen who ground manganese dioxide.[1] The malady was forgotten, until Jaksch[2] in Prague in 1901 demonstrated several such cases in persons employed in a large chemical factory in Bohemia, from the drying of Weldon mud. In the same year three similar cases were also described in Hamburg.[3] In 1902 Jaksch observed a fresh case of poisoning, and in the factory in question described a condition of manganophobia among the workers, obviously hysterical, in which symptoms of real manganese poisoning were simulated. In all some twenty cases are known. Jaksch is of opinion that it is manganese dust rich in manganese protoxide that is alone dangerous, since, if the mud has been previously treated with hydrochloric acid, by which the lower oxides are removed, no illness can be found. The most dangerous compounds are MnO and Mn₃O₄.

PETROLEUM

OCCURRENCE AND USES.—Crude petroleum flows spontaneously from wells in consequence of high internal pressure of gas or is pumped up. In America and Russia also it is conveyed hundreds of miles in conduits to the ports to be led into tank steamers.

The crude oil is a dark-coloured liquid which, in the case of Pennsylvanian mineral oil, consists mainly of a mixture of hydrocarbons of the paraffin series, or, in Baku oil, of those of the naphtha series. There are in addition sulphur compounds, olefines, pyridin, &c. The crude oil is unsuitable for illuminating purposes and is subjected to a distillation process. It is split up into three fractions by a single distillation, namely, (_a_) benzines (boiling-point 150° C.), (_b_) lighting oil (boiling-point 150°-300° C.); at a temperature of 300° C. the distillation is stopped so that (_c_) the residuum boiling above 300° C. remains. Distillation is effected (in America) in large stills, in which periodically benzine and lighting oil up to 300° C. is distilled and the residuum run off. In Baku continuously working batteries of so-called cylindrical boilers are used, into which the crude oil streams. In the first set of boilers, the temperature in which rises to 150° C., the benzine is distilled off, and in the succeeding ones, heated to 300° C., the illuminating petroleum oils (kerosine), the residuum flowing continually away.

The _mineral oil residues_ are used as fuel. Heating by this means, tried first only in Russia, is spreading, especially for the heating of boilers, in which case the liquid fuel is blown in generally as a spray. The combustion if rightly planned is economical and almost smokeless.

The American oil residuum, rich in paraffin, is distilled, the distillate is cooled and separated by pressure into solid paraffin and liquid oil. The latter and the Russian mineral oil residues which are free from paraffin are widely used as lubricants. In the production of lubricants the residues are distilled at low temperature (in vacuo or by aid of superheated steam) and separated into various qualities by fractional cooling, are then purified with sulphuric acid, and finally washed with caustic soda solution.

In the preparation of vaseline the residum is not distilled, but purified only with fuming sulphuric acid and decolourised with animal charcoal.

The _illuminating oil_ is next subjected to a purifying process (refining); it is first treated with sulphuric acid and well agitated by means of compressed air. The acid laden with the impurities is drawn off below, and the oil freed from acid by washing first with caustic soda and subsequently with water. It is then bleached in the sun. For specially fine and high flash point petroleum the oil undergoes a further distillation and purification with acid.

The fractions of crude petroleum with low boiling-point (under 150° C.) are known commercially as raw _benzine_ or _petrol naphtha_. It is used for cleaning, in extraction of fats and oils, and for benzine motors.

Frequently raw benzine is subjected to a purifying process and to fractional distillation. Purification is carried out by means of sulphuric acid and soda liquor and subsequent separation into three fractions and a residue which remains in the retort—(_a_) _petroleum ether_ (called gasoline, canadol, and rhigoline), which comes over between 40° and 70° C., and serves for carburetting water gas and other similar gases, as a solvent for resin, oil, rubber, &c.; (_b_) _purified benzine_ (70°-120° C.) is used as motor spirit and in chemical cleaning; (_c_) _ligroine_ (120°-135° C.), used for illuminating purposes; and (_d_) the _residual oil_ (above 135° C.) serves for cleaning machinery and, especially, as a solvent for lubricating oil, and instead of turpentine in the production of lacquers, varnishes, and oil colours.

In _chemical cleaning_ works benzine is used in closed-in washing apparatus, after which the clothes are centrifugalised and dried. In view of the risk of fire in these manipulations, originating mainly from frictional electricity, various substances are recommended to be added to the benzine, of which the best known is that recommended by Richter, consisting of a watery solution of oleate of sodium or magnesium.

EFFECTS ON HEALTH.—Industrial poisoning in the petroleum industry is attributable to the gases given off from crude petroleum or its products and to inhalation of naphtha dust. Poisoning occurs principally in the recovery of petroleum and naphtha from the wells, in storage and transport (in badly ventilated tanks on board ship, and in entering petroleum tanks), in the refinery in cleaning out petroleum stills and mixing vessels, and in emptying out the residues. Further cases occur occasionally from use of benzine in chemical cleaning.

In addition to poisoning the injurious effect of petroleum and its constituents on the skin must be borne in mind. Opinion is unanimous that this injurious action of mineral oil is limited to the petroleum fractions with high boiling-point and especially petroleum residues.

Statistics officially collected in Prussia show the general health of petroleum workers to be favourable. These statistics related to 1380 persons, of whom forty-three were suffering from symptoms attributable to their occupation. Of these forty-three, nine only were cases of poisoning, the remainder being all cases of petroleum acne.

The conditions also in French refineries from statistics collected in the years 1890-1903 seem satisfactory. Eighteen cases of petroleum acne were reported, eleven of which occurred at the paraffin presses, five in cleaning out the still residues, and two were persons filling vessels.

The conditions are clearly less favourable in the Russian petroleum industry.[1]

The workers at the naphtha wells suffer from acute and chronic affections of the respiratory organs. Those suffer most who cover the wells with cast iron plates to enable the flow of naphtha to be regulated and led into the reservoirs. In doing this they inhale naphtha spray.

Lewin[2] describes cases of severe poisoning with fatal issue among American workers employed in petroleum tanks. One man who wished to examine an outlet pipe showed symptoms after only two minutes. Weinberger describes severe poisoning of two workers engaged in cleaning out a vessel containing petroleum residue.

Interesting particulars are given of the effect of petroleum emanations on the health of the men employed in the petroleum mines of Carpathia, among whom respiratory affections were rarely found, but poisoning symptoms involving unconsciousness and cerebral symptoms frequently. These experiences undoubtedly point to differing physiological effects of different kinds of naphtha.

This is supported by the view expressed by Sharp in America that different kinds of American petroleum have different effects on the health of the workers, which can be easily credited from the different chemical composition of crude naphthas. Thus in Western Virginia, where a natural heavy oil is obtained, asphyxia from the gas is unknown, although transient attacks of headache and giddiness may occur, whereas in Ohio, where light oils are obtained, suffocative attacks are not infrequent. And it is definitely stated that some naphtha products irritate the respiratory passages, while others affect the central nervous system.[3]

The authors mentioned refer to occurrence of cases of poisoning in the refining of naphtha from inhalation of the vapour of the light oils benzine and gasoline. Fatal cases have been recorded in badly ventilated workrooms in which the products of distillation are collected. Workers constantly employed in these rooms develop chronic poisoning, which is reported also in the case of women employed with benzine. Intoxication is frequently observed, it is stated, among the workmen employed in cleaning out the railway tank waggons in which the mineral oils and petroleum are carried.

Foulerton[4] describes severe poisoning in a workman who had climbed into a petroleum reservoir, and two similar cases from entering naphtha tanks are given in the Report of the Chief Inspector of Factories for 1908. Two fatal cases are reported by the Union of Chemical Industry in Germany in 1905 in connection with naphtha stills. Such accidents are hardly possible, except when, through insufficient disconnection of the still from the further system of pipes, irrespirable distillation gases pass backwards into the opened still where persons are working. Ordinary cocks and valves, therefore, do not afford sufficient security. Thus, several workers engaged in repairing a still were rendered unconscious by gases drawn in from a neighbouring still, and were only brought round after oxygen inhalation.

Gowers describes a case of chronic poisoning following on frequent inhalation of gases given off from a petroleum motor, the symptoms being slurring speech, difficulty of swallowing, and weakness of the orbicularis and facial muscles. Gowers believed this to be petroleum gas poisoning (from incomplete combustion), especially as the symptoms disappeared on giving up the work, only to return on resuming it again.[5]

Girls employed in glove cleaning and rubber factories are described as having been poisoned by benzine.[6] Poisoning of chauffeurs is described by several writers.[7]

Recent literature[8] tends to show marked increase in the number of cases of poisoning from greater demand for benzine as a motive power for vehicles. Such cases have been observed in automobile factories, and are attributable to the hydrocarbons of low boiling-point which are present as impurities in benzine.

A worker in a paraffin factory had entered an open benzine still to scrape the walls free of crusts containing benzine. He was found unconscious and died some hours later. It appeared that he had been in the still several hours, having probably been overcome to such an extent by the fumes as to be unable to effect his escape.

Attempt to wipe up benzine spilt in the storage cellar of a large chemical cleaning works resulted in poisoning.

A night worker in a bone extracting works having turned on the steam, instead of watching the process fell asleep on a bench. In consequence the apparatus became so hot that the solder of a stop valve melted, allowing fumes to escape. The man was found dead in the morning. In a carpet cleaning establishment three workers lost consciousness and were found senseless on the floor. They recovered on inhalation of oxygen.

One further case reported from the instances of benzine poisoning collected recently[9] is worth quoting. A worker in a chemical factory was put to clean a still capable of distilling 2500 litres of benzine. It contained remains of a previous filling. As soon as he had entered the narrow opening he became affected and fell into the benzine; he was carried unconscious to the hospital, his symptoms being vomiting, spastic contraction of the extremities, cyanosis, weak pulse, and loss of reflexes, which disappeared an hour and a half later.

The occurrence of skin affections in the naphtha industry has been noted by several observers, especially among those employed on the unpurified mineral oils. Eruptions on the skin from pressing out the paraffin and papillomata (warty growths) in workers cleaning out the stills are referred to by many writers,[10] Ogston in particular.

Recent literature refers to the occurrence of petroleum eczema in a firebrick and cement factory. The workers affected had to remove the bricks from moulds on to which petroleum oil dropped. An eczematous condition was produced on the inner surface of the hands, necessitating abstention from work. The pustular eczema in those employed only a short time in pressing paraffin in the refineries of naphtha factories is referred to as a frequent occurrence. Practically all the workers in three refineries in the district of Czernowitz were affected. The view that it is due to insufficient care in washing is supported by the report of the factory inspector in Rouen, that with greater attention in this matter on the part of the workers marked diminution in its occurrence followed.

SULPHUR

RECOVERY AND USE.—Sulphur, which is found principally in Sicily (also in Spain, America, and Japan), is obtained by melting. In Sicily this is carried out in primitive fashion by piling the rock in heaps, covering them with turf, and setting fire to them. About a third of the sulphur burns and escapes as sulphur dioxide, while the remainder is melted and collects in a hole in the ground.

The crude sulphur thus wastefully produced is purified by distillation in cast-iron retorts directly fired. It comes on the market as stick or roll sulphur or as flowers of sulphur.

Further sources for recovery of sulphur are the Leblanc soda residues (see Soda Production), from which the sulphur is recovered by the Chance-Claus process, and the gas purifying material (containing up to 40 per cent.), from which the sulphur can be recovered by carbon bisulphide (see Illuminating Gas Industry).

The health conditions of the Sicilian sulphur workers are very unsatisfactory, due, however, less to the injurious effect of the escaping gases (noxious alike to the surrounding vegetation) than to the wretched social conditions, over exertion, and under feeding of these workers.

Of importance is the risk to health from sulphuretted hydrogen gas, from sulphur dioxide in the recovery of sulphur from the soda residues, and from carbon bisulphide in the extraction of sulphur from the gas purifying material.

SULPHURETTED HYDROGEN GAS

Sulphuretted hydrogen gas is used in the chemical industry especially for the precipitation of copper in the nickel and cobalt industry, in de-arsenicating acid (see Hydrochloric and Sulphuric Acids), to reduce chrome salts in the leather industry, &c. In addition it arises as a product of decomposition in various industries, such as the Leblanc soda process, in the preparation of chloride of antimony, in the decomposition of barium sulphide (by exposure to moist air), in the treatment of gas liquors, and in the preparation of carbon bisulphide: it is present in blast furnace gas, is generated in mines (especially in deep seams containing pyrites), arises in tar distillation, from use of gas lime in tanning, and in the preparation and use of sodium sulphide: large quantities of the gas are generated in the putrefactive processes connected with organic sulphur-containing matter such as glue making, bone stores, storage of green hides, in the decomposition of waste water in sugar manufacture and brewing, in the retting of flax, and especially in sewers and middens.

Both _acute_ and _chronic_ poisoning are described.

The following case is reported by the Union of Chemical Industry in 1907: Three plumbers who were employed on the night shift in a chemical factory and had gone to sleep in a workroom were found in a dying condition two hours later. In the factory barium sulphide solution in a series of large saturating vessels was being converted into barium carbonate by forcing in carbonic acid gas; the sulphuretted hydrogen gas evolved was collected in a gasometer, burnt, and utilised for manufacture of sulphuric acid. In the saturating vessels were test cocks, the smell from which enabled the workers to know whether all the sulphuretted hydrogen gas had been driven out. If this was so the contents of the retort were driven by means of carbonic acid gas into a subsidiary vessel, and the vessel again filled with barium sulphide liquor. From these intermediate vessels the baryta was pumped into filter presses, the last remains of sulphuretted hydrogen gas being carried away by a fan into a ventilating shaft. The subsidiary vessel and ventilating shaft were situated in front of the windows of the repairing shop. On the night in question a worker had thoughtlessly driven the contents out of one saturating vessel before the sulphuretted hydrogen gas had been completely removed, and the driving belt of the fan was broken. Consequently, the sulphuretted hydrogen gas escaping from the subsidiary vessel entered through the windows of the workshop and collected over the floor where the victims of the unusual combination of circumstances slept.

In another chemical works two workers suffered from severe poisoning in the barium chloride department. The plant consisted of a closed vat which, in addition to the openings for admitting the barium sulphide liquor and sulphuric acid, had a duct with steam injector connected with the chimney for taking away the sulphuretted hydrogen gas. Owing to a breakdown the plant was at a standstill, as a result of which the ventilating duct became blocked by ice. When the plant was set in motion again the sulphuretted hydrogen gas escaped through the sulphuric acid opening. One of the workers affected remained for two days unconscious.[1]

The report of the Union of Chemical Industry for 1905 cites a case where an agitating vessel, in which, by action of acid on caustic liquor, sulphuretted hydrogen gas was given off and drawn away by a fan, had to be stopped to repair one of the paddles. The flow of acid and liquor was stopped, and the cover half removed. The deposit which had been precipitated had to be got rid of next in order to liberate the agitator. The upper portion of the vessel was washed out with water, and since no further evolution of sulphuretted hydrogen was possible from any manufacturing process, the work of removing the deposit was proceeded with. After several bucketfuls had been emptied the man inside became unconscious and died. The casualty was no doubt due to small nests of free caustic and acid which the spading brought into contact and subsequent developement of sulphuretted hydrogen afresh. A case is reported of sulphuretted hydrogen poisoning in a man attending to the drains in a factory tanning leather by a quick process. Here, when sulphurous acid acts on sodium sulphide, sulphuretted hydrogen is given off. In cleaning out a trap close to the discharge outlet of a tannery two persons were rendered unconscious, and the presence of sulphuretted hydrogen was shown by the blackening of the white lead paint on a house opposite and by the odour.[2]

In the preparation of ammonium salts Eulenberg[3] cites several cases where the workers fell as though struck down, although the processes were carried on in the open air. They quickly recovered when removed from the spot.

Oliver cites the case where, in excavating soil for a dock, four men succumbed in six weeks; the water contained 12 vols. per cent. of sulphuretted hydrogen.

Not unfrequently acute poisoning symptoms result to sewer men. Probably sulphuretted hydrogen gas is not wholly responsible for them, nor for the chronic symptoms complained of by such workers (inflammation of the conjunctiva, bronchial catarrh, pallor, depression).

In the distillation processes connected with the paraffin industry fatalities have been reported.

CARBON BISULPHIDE

MANUFACTURE.—Carbon bisulphide is prepared by passing sulphur vapour over pure coal brought to a red heat in cast-iron retorts into which pieces of sulphur are introduced. The crude carbon bisulphide requires purification from sulphur, sulphuretted hydrogen, and volatile organic sulphur compounds by washing with lime water and subsequent distillation.

Use is made of it principally in the extraction of fat and oil from bones and oleaginous seeds (cocoanut, olives, &c.), for vulcanising, and as a solvent of rubber. It is used also to extract sulphur from gas purifying material and for the preparation of various chemical substances (ammonium sulphocyanide, &c.), as well as for the destruction of pests (phylloxera and rats).

Fat and oil are extracted from seeds, bones, &c., by carbon bisulphide, benzine, or ether, and, to avoid evaporation, the vessels are as airtight as possible and arranged, as a rule, for continuous working.

_Vulcanisation_ is the rendering of rubber permanently elastic by its combination with sulphur. It is effected by means of chloride of sulphur, sulphide of barium, calcium, or antimony, and other sulphur-containing compounds, heat and pressure, or by a cold method consisting in the dipping of the formed objects in a mixture of carbon bisulphide and chloride of sulphur. The process of manufacture is briefly as follows: The raw material is first softened and washed by hot water and kneading in rolls. The washed and dried rubber is then mixed on callender rolls with various ingredients, such as zinc white, chalk, white lead, litharge, cinnabar, graphite, rubber substitutes (prepared by boiling vegetable oils, to which sulphur has been added, with chloride of sulphur). In vulcanising by aid of heat the necessary sulphur or sulphur compound is added. Vulcanisation with sulphur alone is only possible with aid of steam and mechanical pressure in various kinds of apparatus according to the nature of the article produced. In the cold vulcanisation process the previously shaped articles are dipped for a few seconds or minutes in the mixture of carbon bisulphide and chloride of sulphur and subsequently dried in warm air as quickly as possible.

In view of the poisonous nature of carbon bisulphide, benzine is much used now. In the cold method use of chloride of sulphur in benzine can replace it altogether.

Instead of benzine other solvents are available—chlorine substitution products of methane (dichlormethane, carbon tetrachloride). In other processes _rubber solvents_ are largely used, for instance, acetone, oil of turpentine, petroleum benzine, ether, and benzene. Rubber solutions are used for waterproofing cloth and other materials.

Similar to the preparation and use of rubber is that of guttapercha. But vulcanisation is easier by the lead and zinc thiosulphate process than by the methods used in the case of rubber.

EFFECTS ON HEALTH OF CS₂ AND OTHER DANGERS TO HEALTH IN THE RUBBER INDUSTRY.—In the manufacture of carbon bisulphide little or no danger is run either to health or from fire.

In the rubber trade the poisonous nature of _benzine_ and _chloride of sulphur_ have to be borne in mind, and also the considerable risk of _lead poisoning_ in mixing. Cases of plumbism, especially in earlier years, are referred to.[1]

_Benzine_ poisoning plays only a secondary part in the rubber industry. No severe cases are recorded, only slight cases following an inhalation of fumes.

Cases of poisoning are recorded in a motor tyre factory in Upsala.[2] Nine women were affected, of whom four died. Whether these cases were due to benzene or petroleum benzine is not stated. It is remarkable that two such very different substances as benzene and benzine should be so easily confused.

But that in the rubber industry cases of benzene poisoning do actually occur is proved by the following recent cases: Rubber dissolved in benzol was being laid on a spreading machine in the usual way. Of three men employed one was rendered unconscious and died.[3]

In a rubber recovery process a worker was rendered unconscious after entering a benzol still, also two others who sought to rescue him. Only one was saved.

Cases of aniline poisoning are reported where aniline is used for extracting rubber.[4]

_Chloride of sulphur_, by reason of its properties and the readiness with which it decomposes (see Chloride of Sulphur), causes annoyance to rubber workers, but rarely poisoning.

Much importance attaches to _chronic carbon bisulphide poisoning_ in the rubber industry. Many scientists have experimented as to its poisonous nature (see especially on this Part II, p. 194).

Lehmann’s[5] experiments show that a proportion of 0·50-0·7 mg. of CS₂ per litre of air causes hardly any symptoms; 1·0-1·2 mg. slight effects which become more marked on continued exposure; 1·5 mg. produces severe symptoms. About 1·0 mg. per litre of air is the amount which may set up chronic effects. In vulcanising rooms this limit may easily be exceeded unless special preventive measures are adopted.

Laudenheimer[6] has made several analyses of the proportion of CS₂ in workrooms. Thus 0·9-1·8 mg. per litre of air were found in a room where pouches were vulcanised; 0·5-2·4 mg. were aspirated one-half metre distant from the dipping vessels; and 0·18-0·27 mg. in the room for making ‘baby comforters.’

In analyses made some years ago proportions of 2·9-5·6 mg. were obtained.

Although literature contains many references to CS₂ poisoning, too much importance ought not to be attached to them now in view of the arrangements in modern well-equipped vulcanising premises. Laudenheimer has collected particulars of 31 cases of brain, and 19 of nervous, diseases among 219 persons coming into contact with CS₂ between 1874 and 1908, all of whom had been medically attended. In the last ten years, however, the psychical symptoms were seven times less than in the preceding period. Between 1896 and 1898 the average proportion of brain disease in the vulcanising department was 1·95 per cent., and of nervous diseases 0·22 per cent., as compared with 0·92 per cent. and 0·03 per cent. in the textile. Moreover, he maintains that practically all workers who come at all into contact with CS₂ must be to some extent affected injuriously by it.

Studies on the injurious nature of CS₂ date from the years 1851-60, when the French writers Pazen, Duchenne, Beaugrand, Piorry, &c., came across cases from the Parkes’ process (cold vulcanisation by means of CS₂ and SCl₂). Delpech[7] published in 1860 and 1863 details of twenty-four severe cases in rubber workers, some of which were fatal, and at the same time described the pitiable conditions under which the work was carried on.

In Germany Hermann, Hirt and Lewin, and Eulenberg dealt with the subject, but their work is more theoretical in character; and in Laudenheimer’s work referred to the histories of several cases are given in detail.

Mention should be made of the injury caused to the skin by the fluids used in extraction of fat and in vulcanising—especially by benzine and carbon bisulphide. Perrin considers the effect due partly to the withdrawal of heat and partly to the solvent action on the natural grease, producing an unpleasant feeling of dryness and contraction of the skin.

ILLUMINATING GAS

Illuminating gas is obtained by the dry distillation of coal. The products of distillation are subjected on the gasworks to several purifying processes, such as condensation in coolers, moist and dry purifying, from which valuable bye-products (such as tar, ammonia, cyanogen compounds) are obtained. The purified gas is stored in gas holders containing on an average 49 per cent. hydrogen, 34 per cent. methane, 8 per cent. carbonic oxide, 1 per cent. carbon dioxide, 4 per cent. nitrogen, and about 4 per cent. of the heavy hydrocarbons (ethylene, benzene vapour, acetylene, and their homologues) to which the illuminating properties are almost exclusively due.

The most important stages in its preparation will be shortly described. _Distillation_ is effected in cylindrical, usually horizontal, fireclay retorts placed in a group or setting (fig. 11), which formerly were heated by coke but in modern works always by gas. Charging with coal and removal of the coke takes place about every four hours, often by means of mechanical contrivances.

Iron pipes conduct the products of distillation to the _hydraulic main_. This is a long covered channel extending the entire length of the stack and receiving the gas and distillate from each retort. In it the greater part of the tar and of the ammoniacal water condense and collect under the water which is kept in the main to act as a seal to the ends of the dip pipes, to prevent the gas from passing back into the retort when the latter is opened. While the liquid flows from the hydraulic main into cisterns, the gas passes into _coolers_ or _condensers_, tall iron cylinders, in which, as the result of air and water cooling, further portions of the tar and ammoniacal liquor are condensed. To free it still more from particles of tar the gas passes through the _tar separator_.

The tar which remains behind flows through a tube to the cistern. From the tar separator the gas goes through _scrubbers_ (fig. 12), where the gas is washed free of ammonia and part of the sulphuretted hydrogen and carbon dioxide with water. The scrubbers are tower-like vessels filled with coke or charcoal through which the gas passes from below upwards, encountering a spray of water. Several scrubbers in series are used, so that the water constantly becomes richer in ammonia. Mechanical scrubbers are much used, so-called standard washers; they are rotating, horizontal cylinders having several chambers filled with staves of wood half dipping in water. In them the same principle of making the gas meet an opposing stream of water is employed, so that the last traces of ammonia are removed from the gas.

The various purifying apparatus through which the gas has to pass cause considerable resistance to its flow. Escape in various ways would occur had the gas to overcome it by its own pressure, and too long contact of the gas with the hot walls of the retorts would be detrimental. Hence an exhauster is applied to the system which keeps the pressure to the right proportion in the retorts and drives on the gas.

After purification in the scrubbers _dry purification_ follows, having for its object especially removal of compounds of sulphur and cyanogen and carbon dioxide. To effect this several shallow receptacles are used, each having a false bottom upon which the purifying material is spread out. The boxes are so arranged that the gas first passes through purifying material which is almost saturated and finally through fresh material, so that the material becomes richer in sulphur and cyanogen compounds. The _gas purifying material_ formerly used was slaked lime, and it is still frequently used, but more generally bog iron ore or artificially prepared mixtures are used consisting mostly of oxide of iron. The saturated purifying material is regenerated by oxidation on spreading it out in the air and turning it frequently. After having been thus treated some ten times the mass contains 50 per cent. sulphur, and 13 to 14 per cent. ferrocyanide.

The _naphthalene_ in illuminating gas does not separate in the condenser, and therefore is generally treated in special apparatus by washing the gas with heavy coal tar.

The gas purified, as has been described, is measured by a meter and stored in gasometers. These are bells made up of sheet iron which hang down into walled receptacles filled with water to act as a water seal, and are raised by the pressure of the gas which streams into them. The gas passes to the network of mains by pressure of the weight of the gasometer, after having passed through a pressure regulating apparatus.

As to recovery of bye-products in the illuminating gas industry, see the sections on Ammonia, Cyanogen Compounds, Tar, Benzene, &c.

EFFECT ON HEALTH.—Opinions differ as to the effect on health which employment in gas works exerts. This is true of old as well as of modern literature.

Hirt[1] maintains that gas workers suffer no increase in illness because of their employment. They reach, he says, a relatively high age and their mortality he puts down at from 0·5 to 1 per cent. (my own observations make me conclude that the average mortality among persons insured in sick societies in Bohemia is 1 per cent., so that Hirt’s figure is not high).

Layet[2] agreed with Hirt, but was of opinion that gas workers suffered from anæmia and gastro-intestinal symptoms attributable to inhalation of injurious gases. The sudden symptoms of intoxication, ‘exhaustion and sinking suddenly into a comatose condition,’ which he attributes to the effect of hydrocarbons and sulphuretted hydrogen gas, may well have been the symptoms of carbonic oxide poisoning.

Goldschmidt[3] in recent literature considers manufacture of illuminating gas by no means dangerous or unhealthy, and speaks of no specific maladies as having been observed by him. Nevertheless, he admits with Layet that the men employed in the condensing and purifying processes are constantly in an atmosphere contaminated by gas, and that the cleaning and regeneration of the purifying mass is associated with inflammation of the eyes, violent catarrh, and inflammation of the respiratory passages, since, on contact of the purifying mass with the air, hydrocyanic acid gas, sulphocyanic acid gas, and fumes containing carbolic, butyric, and valerianic acids are generated.

Other writers[4] refer to the injurious effects from manipulating the purifying material. In general, though, they accept the view, without however producing any figures, that work in gas works is unattended with serious injury to health and that poisonings, especially from carbonic oxide, are rare. Such cases are described,[5] but the authors are not quite at one as to the healthiness or otherwise of the industry. The one opinion is based on study of the sick club reports for several years of a large gas works employing some 2400 workers (probably Vienna).[6] The average frequency of sickness (sickness percentage), excluding accidents, was 48·7 per cent. The conclusion is drawn that the health conditions of gas workers is favourable. It is pointed out, however, that diseases of the respiratory and digestive organs (12·8 and 10·16 per cent. of the persons employed) are relatively high, and that the mortality (1·56 per cent.) of gas-workers is higher than that of other workers. This is attributed to the constant inhalation of air charged with injurious gases. Work at the retorts, coke quenching, and attending to the purifying plant are considered especially unhealthy.

The other figures relate to the Magdeburg gas works; they are higher than those quoted. The morbidity of the gas workers was found to be 68·5 per cent., of which 18 per cent. was due to disease of the digestive system, 20·5 per cent. to disease of the respiratory organs, and 1 per cent. to poisoning. No details of the cases of poisoning are given. Carbonic oxide poisoning is said to be not infrequent, the injurious effect of cleaning the purifiers is referred to, and poisoning by inhalation of ammonia is reported as possible.

Still, no very unfavourable opinion is drawn as to the nature of the work. The sickness frequency in sick clubs is about 50 per cent., and even in well-managed chemical works Leymann has shown it to be from 65 to 80 per cent. The recently published elaborate statistics of sickness and mortality of the Leipzig local sickness clubs[7] contain the following figures for gas workers: Among 3028 gas workers there were on an average yearly 2046 cases of sickness, twenty deaths, and four cases of poisoning. The total morbidity, therefore, was 67·57 per cent., mortality 0·66 per cent., and the morbidity from poisoning 0·13 per cent. Diseases of the respiratory tract equalled 10·63 per cent., of the digestive tract 10·87 per cent., of the muscular system 13·10 per cent., and from rheumatism 11·10 per cent. These figures, therefore, are not abnormally high and the poisoning is very low.

Still, industrial cases of poisoning in gas works are recorded. Of these the most important will be mentioned. Six persons were employed in a sub-station in introducing a new sliding shutter into a gas main, with the object of deviating the gas for the filling of balloons. A regulating valve broke, and the gas escaped from a pipe 40 cm. in diameter. Five of the men were rendered unconscious, and resuscitation by means of oxygen inhalation failed in one case. In repairing the damage done two other cases occurred.[8] In emptying a purifier a worker was killed from failure to shut off the valve.

Besides poisoning from illuminating gas, industrial poisoning in gas works is described attributable, in part at least, to ammonia. Thus the report of the factory inspectors of Prussia for 1904 narrates how a worker became unconscious while superintending the ammonia water well, fell in, and was drowned.

A further case is described in the report of the Union of Chemical Industry for 1904. In the department for concentrating the gas liquor the foreman and an assistant on the night shift were getting rid of the residues from a washer by means of hot water. The cover had been removed, but, contrary to instructions, the steam had not been shut off. Ammonia fumes rushed out and rendered both unconscious, in which condition there were found by the workmen coming in the morning.[9]

In the preparation of ammonium sulphate, probably in consequence of too much steam pressure, gas liquor was driven into the sulphuric acid receiver instead of ammonia gas. The receiver overflowed, and ammonia gas escaped in such quantity as to render unconscious the foreman and two men who went to his assistance.[10]

The use of illuminating gas in industrial premises can give rise to poisoning. Thus the women employed in a scent factory, where so-called quick gas heaters were used, suffered from general gas poisoning.[11]

In Great Britain in 1907 sixteen cases of carbonic oxide poisoning from use of gas in industrial premises were reported.

COKE OVENS

Coke is obtained partly as a residue in the retorts after the production of illuminating gas. Such _gas coke_ is unsuitable for metallurgical purposes, as in the blast furnace. Far larger quantities of coal are subjected to dry distillation for metallurgical purposes in coke ovens than in gas works. Hence their erection close to blast furnaces. In the older form of coke oven the bye-products were lost. Those generally used now consist of closed chambers heated from the outside, and they can be divided into coke ovens which do, and those which do not, recover the bye-products. These are the same as those which have been considered under manufacture of illuminating-gas—tar, ammonia, benzene and its homologues, cyanogen, &c. In the coke ovens in which the bye-products are not recovered the gases and tarry vapours escaping on coking pass into the heating flues, where, brought into contact with the air blast, they burn and help to heat the oven, while what is unused goes to the main chimney stack.

A, A´ Coal to be coked; B, B´ Standpipes; C Hydraulic main; D Condensing apparatus; E Purified gas: F, F´ Air inlets; G G,´ G´´ Combustion chambers.]

In the modern _distillation ovens_ with recovery of the bye-products the gases escaping from the coal are led (air being cut off as completely as possible) through ascending pipes into the main collector, where they are cooled, and the tarry ingredients as well as a part of the ammonia are absorbed by water; subsequently the gases pass through washing apparatus with a view to as complete a recovery of the ammonia and benzene as possible. The purified gases are now again led to the ovens and burnt with access of air in the combustion chambers between two ovens. Generally these ovens are so constructed as to act as non-recovery ovens also (especially in starting the process).

The coal is charged into the ovens through charge holes on the top and brought to a level in the chambers either by hand or mechanically. Removal of the coke block after completion of the coking operation is done by a shield attached to a rack and pinion jack. Afterwards the coke is quenched with water.

Recovery of the _bye-products_ of coke distillation ovens is similar to the method described for illuminating gas, i.e. first by condensation with aid of air or water cooling, then direct washing with water (generally in scrubbers), whereby tar and ammonia water are recovered. _Recovery of benzene_ and its homologues (see Benzene later) depends on the fact that the coke oven gases freed from tar and ammonia are brought into the closest possible contact with the so-called wash oils, i.e. coal tar oils with high boiling-point (250-300° C.). For this purpose several washing towers are employed. The waste oil enriched with benzene is recovered in stills intermittently or continuously and used again.

EFFECTS ON HEALTH.—Injury to health from work at coke ovens is similar to that in the manufacture of illuminating gas. There is the possibility of carbonic oxide poisoning from escape of gas from leakage in the apparatus. As further possible sources of danger ammonia, cyanogen and sulpho-cyanogen compounds, and benzene have to be borne in mind.

In the distillation of the wash oil severe poisoning can arise, as in a case described, where two men were fatally poisoned in distilling tar with wash oil.[1]

The details of the case are not without interest. The poisoning occurred in the lavatory. The gases had escaped from the drain through the ventilating shaft next to the closet. The gases came from distillation of the mixture of tar and wash oil, and were driven by means of air pumps in such a way that normally the uncondensed gases made their way to the chimney stack. On the day of the accident the pumps were out of use, and the gases were driven by steam injectors into the drain. Analysis showed the gases to contain much sulphuretted hydrogen. When this was absorbed, a gas which could be condensed was obtained containing carbon bisulphide and hydrocarbons of unknown composition (? benzene). Only traces of cyanogen and sulpho-cyanogen compounds were present. Physiological experiment showed that poisoning was attributable mainly to sulphuretted hydrogen gas, but that after this was removed by absorption a further poisonous gas remained.

Other Kinds of Power and Illuminating Gas

_Producer gas_ or _generator gas_.—Manufacture of producer gas consists in dealing separately with the generation of the gas and the combustion of the gases which arise. This is effected by admitting only so much air (primary air supply) to the fuel as is necessary to cause the gases to come off, and then admitting further air (secondary supply) at the point where the combustion is to take place; this secondary supply and the gas formed in the gas producer are heated in regenerators before combustion by bringing the gases to be burnt into contact with _Siemens’s heaters_, of which there are four. Two of these are always heated and serve to heat the producer gas and secondary air supply.

A producer gas furnace, therefore, consists of a gas producer, a gas main leading to the furnace hearth, the heater, and the chimney.

The gas producer is a combustion chamber filled with coal in which the coal in the upper layer is burnt. Generators may have horizontal or sloping grate (see figs. 15 and 16). The _Siemens’s_ heaters or regenerators are chambers built of, and filled loosely with, fireclay bricks and arranged in couples. Should the gas producers become too hot, instead of the chambers subdivided air heaters are used, whereby the hot furnace gases are brought into contact with a system of thin-walled, gastight fireclay pipes, to which they give up their heat, while the secondary air supply for the furnace is led beside these pipes and so becomes heated indirectly. Previous heating of the producer gas is here not necessary; no valves are needed because the three streams of gas all pass in the same direction.

L Air; G Gas

FIG. 17B.—Siemens’s Regenerative Furnace]

Such air heating arrangements are used for heating the retorts in gas works, for melting the ‘metal’ in glass works, and very generally in other industries, as they offer many technical and hygienic advantages. Generator gas from coke contains 34 per cent. carbonic oxide, 0·1 per cent. hydrogen, 1·9 per cent. carbon dioxide, and 64 per cent. nitrogen.

_Blast furnace gas._—Blast furnace gas is formed under the same conditions as have been described for generator gas; it contains more carbon dioxide (about 10 per cent.). (Further details are given in the section on Iron—Blast Furnaces.)

_Water gas._—Water gas is made by the passage of steam through incandescent coal, according to the equation:

C + H₂O = CO + 2H.

The iron gas producer, lined with firebrick, is filled with anthracite or coke and heated by blowing hot air through it. This causes producer gas to escape, after which steam is blown through, causing water gas to escape—containing hydrogen and carbonic oxide to the extent of 45-50 per cent., carbon dioxide and nitrogen 2-6 per cent., and a little methane.

The blowing of hot air and steam is done alternately, and both kinds of gas are led away and collected separately, the water gas being previously purified in scrubbers, condensers, and purifiers. It serves for the production of high temperatures (in smelting of metals). Further, when carburetted and also when carefully purified in an uncarburetted state, it serves as an illuminant. The producer gas generated at the same time is used for heating purposes (generally for heating boilers).

_Dowson gas._—Dowson gas is obtained by collecting and storing together the gases produced in the manner described for water gas. Under the grating of the wrought-iron gas producer (lined with firebrick and similarly filled with coke or anthracite) a mixture of air and steam, produced in a special small boiler, is blown through by means of a Körting’s injector.

Before storage the gas is subjected to a purifying process similar to that in the case of water gas. The mixed gas consists of 1 vol. water gas and 2-3 vols. producer gas, with about 10-15 vols. per cent. H, 22-27 vols. per cent. CO, 3-6 per cent. CO₂, and 50-55 per cent. N. It is an admirable power gas for driving gas motors (fig. 18).

_Mond gas_ similarly is a mixed gas obtained by blowing much superheated steam into coal at low temperature. Ammonia is produced at the same time.

A Steam boiler
a Steam injector
B Furnace
b Charging hopper
c Cover g
d Valve C
e Cock D
f Vent pipe
g Steam Pipe
C Washer
D Coke tower
E Sawdust purifier]

_Suction gas._—In contradistinction to the Dowson system, in which air mixed with steam is forced into the producer by a steam injector, in the suction gas plant the air and steam are drawn into the generator by the apparatus itself. The whole apparatus while in action is under slight negative pressure. A special steam boiler is unnecessary because the necessary steam is got up in a water container surrounding or connected with the cover of the generator. The plant is set in motion by setting the fire in action by a fan.

Fig. 19 shows a suction gas plant. B is the fan. Above the generator A and at the lower part of the feed hopper is an annular vessel for generating steam, over the surface of which air is drawn across from the pipe e, passing then through the pipe f into the ash box g, and then through the incandescent fuel. The gas produced is purified in the scrubber D, and passes then through a pipe to the purifier containing sawdust and to the motor.

_Carburetted gas._—Gas intended for illuminating purposes is carburetted to increase its illuminating power, i.e. enriched with heavy hydrocarbons. Carburetting is effected either by a hot method—adding the gases distilled from mineral or other oils—or by a cold method—allowing the gas to come into contact with cold benzol or benzine. Coal gas as well as water gas is subjected to the carburetting process, but it has not the same importance now in relation to illuminating power, as reliance is more and more being placed on the use of mantles.

ACETYLENE

_Calcium carbide._—Acetylene is prepared from calcium carbide, which on contact with water gives off acetylene.

_Calcium carbide_ is prepared electro-chemically. A mixture of burnt lime and coke is ground and melted up together at very high temperature in an electric furnace, in doing which there is considerable disengagement of carbonic oxide according to the equation:

CaO + 3C = CaC₂ + CO.

The furnaces used in the production of calcium carbide are of different construction. Generally the furnace is of the nature of an electric arc, and is arranged either as a crucible furnace for intermittent work or like a blast furnace for continuous work.

Besides these there are resistance furnaces in which the heat is created by the resistance offered to the passage of the current by the molten calcium carbide.

The carbonic oxide given off in the process causes difficulty. In many furnaces it is burnt and so utilised for heating purposes. The calcium carbide produced contains as impurities silicon carbide, ferro-silicon, calcium sulphide, and calcium phosphide.

_Acetylene_ (C₂H₂), formed by the decomposition of calcium carbide by means of water (CaC₂ + 2H₂O = Ca(OH)₂ + C₂H₂), furnishes when pure an illuminating gas of great brilliancy and whiteness. Its production is relatively easy. Used for the purpose are (1) apparatus in which water is made to drop on the carbide, (2) apparatus in which the carbide dips into water and is removed automatically on generation of the gas, (3) apparatus in which the carbide is completely immersed in water, and (4) apparatus in which the carbide in tiny lumps is thrown on to water. These are diagrammatically represented in figs. 20A to 20D.

FIG. 20B.

FIG. 20C.

FIG. 20D.

Acetylene Apparatus—diagrammatic (_after Lueger_) A Dripping; B Dipping; C Submerging; D Throwing in]

The most important impurities of acetylene are ammonia, sulphuretted hydrogen gas, and phosphoretted hydrogen. Before use, therefore, it is subjected to purification in various ways. In Wolf’s method the gas is passed through a washer (with the object of removing ammonia and sulphuretted hydrogen gas) and a purifying material consisting of chloride of lime and bichromate salts. In Frank’s method the gas passes though a system of vessels containing an acid solution of copper chloride, and also through a washer. Chloride of lime with sawdust is used as a purifying agent. Finally, the gas is stored and thence sent to the consumer (see fig. 21).

EFFECTS ON HEALTH.—Almost all the poisoning caused in the industries in question is due to carbonic oxide gas, of which water gas contains 41 per cent., generator gas 35 per cent., and suction and Dowson gas 25 per cent.