Chapter LXIX: Part 2 (30)

The arrangements for preparing sulphurous acids are retorts, into which are put sulphuric acid and pieces of wood; upon the application of heat the sulphurous acid passes off, and is conveyed by leaden pipes into the vessels containing the tallow. The lime soap formed is then moistened with 12 cwt. of sulphuric acid, at 150° Fahr., diluted with 50 gall. of water. The whole is thoroughly agitated and the steam cautiously admitted, so as not to dilute the acid too much until the decomposition is general at all points. This occupies about 3 hours, and in 2 or 3 hours more the sulphate of lime has collected at the bottom, while the fatty acids are floating on the surface of the solution of the bisulphate of lime. Several processes of washing with steam and water are necessary to ensure the removal of the sulphate of lime, &c., and after settling for 4 hours the fatty acids are forced through a fixed siphon, into a vat, where they are again washed with water; they are then siphoned at last into a trough lined with lead, on the bottom of which are placed leaden gutters, pierced below by long pegs of wood. The fatty acids are then placed in clothes and subjected to pressure in the stearin cold press.

In 1871 Professor Boek of Copenhagen, after a careful microscopic and chemical investigation, discovered that the neutral fats were composed of a congeries of little globules enclosed in albuminous envelopes. To the presence of these latter substances in the fat he attributed the difficulty of eliminating the fatty acids from it by means either of sulphuric acid, except in excess, or of alkali, except under great pressure; conceiving that both these agents as employed under the usual methods were expended in rupturing and destroying the albuminous coverings.

The inconveniences arising from the above processes are, in the case of the excess of the sulphuric acid, a considerable destruction of the fatty acid, as well as the necessity of its distillation, and the consequent danger of conflagration; whilst in the case of the alkali, this must either be used in quantities much greater than theory requires, or else be heated under great pressure, at the risk of giving rise to an explosion.

In Professor Boek’s process these dangers, together with the waste of material, are avoided. By submitting the fat for a limited time and at a given temperature to the action of a small quantity of sulphuric acid, the albuminous envelopes are broken and partly destroyed. The neutral fat thus liberated is then placed in open tanks in water, by which, after the expiration of several hours, it becomes decomposed. When this is completely effected the glycerin, dissolved in the water used for the decomposition, is removed; the fatty acids which remain behind, and which amount to 94 per cent. of the original fat, being at this stage of the operation dark brown or blackish in colour.

In this condition they are placed in open tanks, and dilute solutions of certain agents are poured upon them, whereby the albuminous débris as well as the colouring matters with which they are associated become oxidised, whilst the specific gravity of these latter is in consequence so increased as to cause them to subside to the bottom of the tank, leaving the fatty acids, now greatly whitened, on the upper part of the liquid.

The acids after being washed 2 or 3 times with dilute acid and water are then cooled, and hot-pressed in the usual manner, and the stearic acid thus obtained is said to have a higher melting point, and to be larger in yield than that obtained by any other method, an oleic acid of excellent quality being at the same time produced.

In 1874 a French patent was taken out for an improvement in the manufacture of stearic acid. The patentee employs carbon disulphide to increase the fluidity of the oleic acid, so that the warm pressure of the crude stearic acid is avoided. The addition of the carbon disulphide may be made either before or after the cold pressing of the stearic acid. The crude fat acid is melted in a special apparatus, and 20 per cent. of the disulphide is mixed with it whilst in the fluid state. It is then left to cool and subjected to cold pressure. The stearic acid thus obtained should be free from oleic acid.

_Prop., &c._ Pure stearic acid crystallises in milk-white needles, which are soluble in ether and in cold alcohol, and forms salts with the bases, called stearates. The commercial acid is made into candles. See CANDLES, FAT, OILS (Fixed), and TALLOW.

=STE′ARIN.= C_{57}H_{110}O_{6}. The solid portion of fats which is insoluble in cold alcohol.

_Prep._ Pure strained mutton suet is melted in a glass flask along with 7 or 8 times its weight of ether, and the solution allowed to cool; the soft, pasty, semi-crystalline mass is then transferred to a cloth and is strongly pressed as rapidly as possible, in order to avoid unnecessary evaporation; the solid portion is then redissolved in ether, and the solution allowed to crystallise, as before. The product is nearly pure.

_Prop., &c._ White; semi-crystalline; insoluble in water and cold alcohol; soluble in 225 parts of cold ether, and freely so in boiling ether. It melts at 130° Fahr. The stearin of commerce is stearic acid.

=STEAROP′TEN.= The name given by Herberger to the concrete portion or camphor of volatile oils. Bizio calls it stereusin.

=STEEL.= This important material may be defined as iron chemically combined with sufficient carbon to give it extreme toughness and hardness without brittleness. According to one of our greatest authorities on metallurgy, steel should contain from ·833% to 1·67% of carbon, these numbers referring respectively to the softest and the hardest varieties.

By some authorities silicon in small quantities is supposed to be a useful ingredient in steel, and to increase its capacity for being hardened; an opinion dissented from by others, who hold that its presence has a tendency to interfere with the welding of the metal. Faraday and Stodart believed that the addition of small quantities of chromium and iridium to steel served to improve its quality, and the same has been asserted of tungsten and titanium; but on these points there is still a divergence of opinion, and no satisfactory decision has yet been arrived at concerning them.

Manganese has also been credited with the property of improving steel, but as it has been found that only a very minute quantity of the manganese is taken up by the steel, an indirect influence may possibly be exercised by it, viz. its power of uniting with the stage, and of carrying away any prejudicial excess of sulphur and phosphorus with it; and in this manner it may contribute to the increased purity of the metal. The addition of manganese to cast steel constitutes Mr Heath’s patent, the chief advantage of which is that blistered steel made from British bar iron can be substituted for the much more expensive Swedish and Russian iron, in certain branches of iron manufacture.

“Among the various substances which are frequently present in malleable iron and in cast iron, those which are more prejudicial to the quality of steel are sulphur, phosphorus, and copper. The amount of sulphur in steel of the best quality rarely exceeds ·012; within the limit of ·1 per cent. it is considered to render the metal more capable of being welded at a moderate heat, but to make it red short. Phosphorus also renders steel more capable of being welded, and at the same time makes its cold short when it amounts to ·1 per cent. The best steel rarely contains so much. Copper renders steel decidedly red short when present in very small amount, and for this reason iron smelted from ores containing copper pyrites is not suitable for making steel.”[195]

[Footnote 195: Payen.]

Within the last few years great attention has been paid to the investigation of the chemistry of steel. The researches of Despretz and Fremy tend to the conclusion that nitrogen exercises a very important influence over the phenomena of ‘steeling,’ and that carbon plays a less necessary part; while those of Caron and Deville still refer the formation of steel to the chemical combination of iron with carbon. There is no test of the value of steel beyond its elasticity and temper, and the fineness, equality, and smoothness of its grain.

Cast iron, wrought iron, and steel are all combinations of iron and carbon, differing in the amount they contain of the latter element. As cast iron contains a larger and wrought iron a smaller proportion of carbon than steel, it follows that to convert the cast iron into steel, its excess of carbon must be removed; whilst conversely, to make the wrought iron into steel, the requisite amount of carbon must be added to it.

Thus it is that the various processes for the manufacture of steel (with the exception of those which propose to obtain it direct from the ores) are directed to one or other of these ends, viz. the decarburation of cast or pig iron, and the carburation of wrought or malleable iron.

1. In the first, or decarburation method, the oxygen of the air plays an important part. Best carbon is heated with coal or charcoal, in some works on the refining hearth, in others upon the bed of the puddling furnace. The oxygen burnt off the excess of carbon from the iron and steel is left. Payen says that when the iron contains slag, the ferrous silicate present in this takes part in the reaction.

The steel obtained by this method is called natural steel. It is afterwards subjected to forging, and being of inferior quality is employed in the manufacture of springs for machinery, railway carriages, wheel tyres, ploughs, and other farming implements.

_The following Table, from ‘Payen’s Industrial
Chemistry’ gives the Composition of several kinds of
Steel._

+--------------+---------+------+------+------+---------------+
| | | | | | Carbon. |
| | | | | +------+--------+
|Kind of Steel.|Locality.| Fe. | Mn. | Cu. |Comb- |Graphi- |
| | | | | |ined. | tic. |
+--------------+---------+------+------+------+------+--------+
|Natural Steel |Siegen | ... | ... |·379 |1·698 | ... |
|Ditto |Solingen | ... | ... | ... |1·570 | ... |
|Puddled Steel |Hartz | ... |0·12 | ... |1·380 | ... |
|Cement Steel |English | ... | ... | ... |1·807 | ... |
|Ditto |German | ... | ... | ... | ·416 | ·080 |
|Cast Steel |Sheffield| ... | ... | ... | ·950 | ·220 |
|Ditto |Ditto | ... | ... | ... | 1·758 |
|Ditto |French | ... | ... | ... | ·65 |
|Sword Steel |Damascus | ... | ·070 | ... | 1·089 |
|Ditto |Ditto | ... |trace | ... | ·775 |
|Wootz |Indian | ... | ... | ... | 1·500 |
|Ditto |Ditto |98·092| ... | ... |1·333 ·312 |
|Cast Steel |German | ... |trace |·300 | 1·180 |
|Ditto |English | ... |·024 |·066 | 1·275 |
|Bessemer Steel|Dowlais | ... |·576 |·025 | ·490 |
|Ditto |Sweden | ... |trace | ... | ·085 |
|Ditto | ... | ... |·179 | ... | ·300 |
|Ditto | ... | ... |·256 | ... | ·700 |
|Ditto | ... | ... |·468 | ... | ·950 |
|Ditto | ... | ... |·355 | ... | 1·050 |
|Wired |Barrow- | ... |·214 | ... | ·200 |
| |in-Furness | | | |
|Rail Heads |German | ... |·386 | ... | ·138 |
|Rails | ... | ... |·264 | ... | ·150 |
|Ditto | ... | ... |·638 | ... | ·046 |
|Boiler Plates | ... | ... |·136 | ... | ·250 |
|Ditto | ... | ... |·273 | ... | ·300 |
+--------------+---------+------+------+------+---------------+

+--------------+-----+-------+-----+----------+
|Kind of Steel.| Si. | S. | P. |Authority.|
+--------------+-----+-------+-----+----------+
|Natural Steel |·038 | ... | ... |Karsten. |
|Ditto |·020 | ... | ... |Lampadius.|
|Puddled Steel |·006 |(at·12)|trace|Brauns. |
|Cement Steel |·100 | ... | ... |Berthier. |
|Ditto | ... | ... | ... |Bromeis. |
|Cast Steel | ... | ... | ... |Ditto. |
|Ditto | ... | ... | ... |Karsten. |
|Ditto |·040 | ... | ... | ... |
|Sword Steel | ... |(Ni·07 Wo·01)| ... |
|Ditto | ... |(Ni·21 | ... |
| | |Co trace | |
| | |Wo trace) | |
|Wootz |·600 | ... | ... | ... |
|Ditto |·045 |(as 037) ... |Henry. |
|Cast Steel |·330 |(Ni ·12) ·020| ... |
|Ditto |·213 |(as·007) ...| ... |
|Bessemer Steel|·009 |·003 | ·036| ... |
|Ditto |·008 |trace | ·025|Brusewitz.|
|Ditto |·044 | do. | ·033| Ditto. |
|Ditto |·032 | do. | ...| Ditto. |
|Ditto |·047 | do. | ·032| Ditto. |
|Ditto |·067 | do. | ...| Ditto. |
|Wired |·179 |·030 | ·026| Ditto. |
|Rail Heads |·306 |·040 | ·034| Ditto. |
|Rails |·091 |·025 | ·032| Ditto. |
|Ditto |·634 |·045 | ·093| Ditto. |
|Boiler Plates |·016 |·010 | ... | Ditto. |
|Ditto |·056 |·040 | ·041| Ditto. |
+--------------+-----+-------+-----+----------+

Krupp’s cast steel, manufactured at Essen, near Cologne, is a natural steel, being made on the bed of a puddling furnace. It is obtained from hæmatite and spathic ore, coke being used for the smelting. The proportion of carbon in Krupp’s steel is about 1·2 per cent. When required for ordnance it is fused with a little bar iron in pots, each of which holds 30 lbs. It sometimes happens that in the manufacture of a huge gun or cannon the contents of as many as 1200 of these pots are required. When this is the case the pots are emptied of their molten contents simultaneously into a channel leading to the cast, 400 well-drilled men being required to carry out the operation.

It is very essential that castings of such magnitude should be allowed to cool very gradually. They are therefore enveloped in hot cinders for two or three months, after which they are ready for the forging.

2. _The carburation method._ This is generally effected by the process known as ‘cementation,’ which is carried out as follows:——Two chests, made of fire-brick or stone, one narrow end of each of which is shown in the accompanying plate, are so fixed in a dome-shaped furnace, so that the flames from the hearth beneath can effectually play around them.

The process renders it necessary that the temperature of the furnace should be steadily maintained for some days; and this is achieved by surrounding the furnace with a conical wall of brick-work, as shown in the cut. The chests are usually about 10 or 12 feet in length, 3 feet in height, and 3 feet in depth. A layer of charcoal of a fineness to pass through a sieve of a 1/4 inch mesh, or of soot, is placed on the bottom of each chest, and upon this the bars of wrought iron which are intended for conversion into steel. The bars inside must be of iron of the best quality, and generally about 3 inches broad and 3/4 of an inch thick. When arranged regularly a little distance apart, the interstices between them are filled up with charcoal, with which they are then covered to a depth of about an inch. Similar layers of bars, similarly arranged, succeed to this first one, until the chests are filled.

They are then covered in to a depth of 6 inches with a luting of damp clay or sand. Each chest when thus filled contains from 5 to 6 tons of iron. One of the bars projects through an opening at the end of the chest, to facilitate an inspection of it from time to time by a workman, so that he may be enabled to judge of the progress of the operation. The materials of which the chests are composed render it important that the temperature of the furnace should be carefully and gradually increased, as a too sudden accession of heat would lead to the splitting of the chests. The temperature necessary to effect the carburation of the iron has been found to be that required for the melting of copper, viz. 1996° Fahr. When this temperature is reached it is maintained for eight or ten days, or even longer, the period depending upon the thickness of the iron, and the degree of hardness it is desired it shall possess. Six or eight days are sufficient to yield steel of a moderate degree of hardness. At the end of the requisite time the fire is gradually put out, and the chests as gradually cooled, a process which occupies about another ten days.

The effect of the treatment to which the iron bars have been subjected has been, in the first place, to entirely alter their interior structure; for if they are broken asunder at any part, instead of showing the fibrous arrangement observable in bar iron, they present a closely granular one. In the second place, chemical analyses demonstrate that the iron has combined with about 1 per cent. of carbon, and that this combination has not only taken place on the surface of the bar, but has extended throughout its whole substance. It is because of this perfect impregnation of the iron by the solid carbon that the process by which it has thus been converted into steel is called ‘cementation.’

Two suggestions have been offered in explanation of the blistered surface presented by the steel. One of these, the theory of Mr T. H. Henry, is that part of the carbon in penetrating into the body of the bar iron had combined with the small quantity of sulphur present in the iron, and that the bisulphide of carbon thus formed becoming vaporised by the elevated temperature, in escaping through the soft surface of the metal, has caused its blistered condition. The second conjecture is that the blebs have arisen from the extrication of carbonic oxide, which had been formed in the bar by the union of the carbon with the small quantity of oxide of iron or slag accidentally remaining in it.

Graham has shown that soft iron has the power of absorbing or occluding at a low red heat 4·15 times its volume of carbolic oxide, which the metal, when it becomes cold, retains, but which it parts with when subjected to a temperature such as that which prevailed in the cementation box. This fact seems to offer a reasonable confirmation of the reaction it has been surmised takes place during the cementation process, and which is supposed to be as follows:

The small quantity of atmospheric oxygen remaining in the chest unites with the carbon to form carbonic oxide. This carbonic oxide gives up half its carbon to the iron (which thereby becomes converted into steel), and in doing so changes to carbonic acid, which becomes reduced to carbonic oxide by the absorption of more carbon from the charcoal, which carbon the carbonic oxide again transfers to the iron.

The above reaction may not improbably occur throughout the substance of the bar. By some chemists, cyanogen compounds are supposed to be present in the cementation powder, and the cyanogen contained in these is supposed to be the carrier of the carbon to the iron.

“The blistered steel obtained by this process is, as would be expected, far from uniform, either in composition or texture; some portions of the bar contain more carbon than others, and the interior contains numerous cavities. In order to improve its quality it is subjected to a process of fagotting similar to that employed in the case of bar iron; the bars of blistered steel, being cut into short lengths are made up into bundles, which are raised to a welding heat, and placed under a tilt hammer weighing about 2 cwt., which strikes 200 or 300 blows in a minute; in this way, the several bars are consolidated into one compound bar, which is then extended under the hammer till of the required dimensions.

“The bars, before being hammered, are sprinkled with sand, which combines with the oxide of iron upon the surface, and forms a vitreous layer which protects the bar from oxidation. The steel which has been thus hammered is much denser and more uniform in composition; its tenacity, malleability, and ductibility are greatly increased, and it is fitted for the manufacture of shears, files, and other tools. It is commonly known as shear steel. Double shear steel is obtained by breaking the tilted bars in two, and welding these into a compound bar. The best variety of steel, however, which is perfectly homogeneous in composition, is that known as cast steel, to obtain which about 30 lbs. of blistered steel are broken into fragments, and fused in a fire-clay or plumbago crucible, heated in a wind furnace, the surface of the metal being protected from oxidation by a little glass melted upon it. The fused steel is cast into ingots, several crucibles being emptied simultaneously into the same mould. Cast steel is far superior in density and hardness to shear steel, but, since it is exceedingly brittle at a red heat, great care is necessary in forging it. It has been found that, in addition to 100 parts of the cast steel, of one part of a mixture of charcoal and oxide of manganese, produces a very fine grained steel, which admits of being cast on to a bar of wrought iron in the ingot mould, so that the tenacity of the latter may compensate for the brittleness of the steel; when the compound bar is forged, the wrought iron forming the back of the implement, and the steel its cutting edge.”[196]

[Footnote 196: Bloxam’s ‘Chemistry Inorganic and Organic.’]

Another distinct method from the cementation one, by which the carburation of iron is affected, is that in which scrap or malleable iron is mixed with pig or cast iron, this latter being fused with the scrap iron in quantity sufficient to afford such an amount of carbon as is necessary to convert the mixture into steel. Steel made by this operation is entirely homogeneous, the tilting process which precedes the casting of the steel obtained by cementation is therefore unnecessary. The pig iron is placed on the bed (made of refractory sand) of one of Siemens’ regenerative furnaces, heated by gaseous fuel. The temperature in this furnace is so intense that the pig iron becomes perfectly liquid, and, when in this condition, the scrap iron, which has been previously heated to redness in an adjoining refractory furnace, is added, it becomes dissolved by it. Iron may also be carburetted by heating wrought iron bars in carburetted hydrogen. This process, however, is seldom had recourse to.

In the manufacture of Bessemer steel both the carburation and decarburation processes are practised. From 1 to 5 tons of pig or cast iron in a molten state are run from a contiguous blast, cupola, or reverberatory furnace, with an apparatus known as a converter, which is previously heated up to redness by means of coke. The converter is figured under two aspects in the annexed engraving.

This vessel, which is generally made of boiler plates of sheet iron, has an inside lining, consisting of a siliceous fireproof material, and is perforated at the bottom with a number of concentric little openings, which are the orifices of as many little tubes or tuyeres, that lead into an outside main tube, as shown in the plate. By means of these tubes condensed air is forced into the mass of melted metal, which is soon thrown into violent commotion, and sends out a shower of ignited sparks. The oxide of iron formed at the same time being set into active movement by the incoming blast of air, is brought into intimate contact with every particle of the carbon and silicon contained in the cast iron, and converts the former into carbonic oxide, which burns with its characteristic flame at the mouth of the converter, and the silica into silicic acid, which enters into the slag, and floats, in the form of foam, on the top of the heavier molten iron.

The removal of the carbon (which is known by the discontinuance of the carbonic oxide flame) being thus accomplished, the iron has next to be submitted to the carburetting operation. This is performed by running into the liquid iron in the converter such a quantity of molten pig or cast iron as contains the required proportion of carbon.

The pig iron used for this purpose generally contains, in addition to a large amount of carbon, a very perceptible quantity of manganese. The converter (as shown in the plate) is then by means of the trunnion tilted, so that its contents can be run into a ladle and transferred to the necessary moulds. The time of conversion occupies from ten to twenty minutes.

By Bessemer’s process the sulphur present in the pig iron is almost entirely eliminated; the greater part of the silicon is also separated, together with the carbon, and almost in the same proportion; but the phosphorus is not removed, and, owing to the oxidation of some iron, the amount is actually greater in the finished steel than in the pig iron.[197]

[Footnote 197: Payen’s ‘Industrial Chemistry,’ edited by B. H. Paul, Ph.D.]

Bessemer’s steel is in large demand, and is excellently suited for rails for railroads, cannon, boiler plates, armour plates, and similar heavy material, for the manufacture of which it has largely supplanted wrought iron, but not at all adapted for the manufacture of knives, razors, lancets, or similar instruments, in which a sharp or keen edge is desirable.

The Bessemer process, which is largely adopted by the manufacturers of steel throughout Europe and America, has proved a source of princely income to its inventor, who obtains a bounty of a shilling on every ton of steel made by it. In Europe alone in 1859 5-1/2 million cwts. Seventy per cent. of this quantity was the produce of British industry.

Latterly, attempts have been made to obtain steel direct from the ores. The efforts made in this direction have been greatly stimulated by the invention of the regenerating furnace of Siemens. In these furnaces, in which an intense temperature is obtained by means of the combustion of inflammable gases (chiefly consisting of carbonic oxide, hydrogen, and carburetted hydrogen), the ore after (in one process) being melted in hoppers by means of the burning gases, runs down, and is gradually dissolved in some melted pig iron placed on the hearth of the furnace. When this latter has been sufficiently diluted with the decarbonised iron the operation is complete.

_Properties of Steel._ The effects of temperature upon steel are remarkable, and a knowledge of them has proved of great practical utility in the manufacture of the various steel-ware articles that are so indispensable to our every-day wants and needs. If forged and soft steel is heated, and then suddenly cooled, it becomes hard, the hardness varying with the temperature and the rapidity with which this has been reduced. The higher the temperature and the more rapidly it is cooled, the greater will be its hardness. Steel, which has been heated until white-hot, and then suddenly plunged into a bath of cold mercury, acquires a hardness nearly equalling that of the diamond. That, however, which the steel gains in hardness, it loses in pliancy and elasticity, besides becoming so brittle as to be of no possible use.

Soft steel, which has been made hard by heating it to redness, and by subsequent sudden immersion in cold water, may be reconverted into soft steel by again heating it to redness and allowing it to cool suddenly. By stopping short, however, of heating it to redness, its hardness may be proportionally modified.

Hence steel articles, varying as much in the qualities of hardness and elasticity as a lancet and watch-spring, are made either by ‘heating down’ hard steel to requisite temperature and allowing it to cool, or by ‘heating up’ soft steel to the necessary point and also letting it gradually cool. When steel is so treated it is said to be _tempered_ or _annealed_. If polished steel be heated over a flame to a temperature of 430° F. its surface becomes of a very pale yellow colour; the colour passes through different shades of yellow and blue with each successive increase of temperature, until when raised to 600° F. it becomes blackish blue.

These effects are due to the formation on the surface of the steel of films of oxide of different degrees of thickness, and to the action of the light on these. They are precisely analogous to those which are caused when a ray of reflected light falls upon any other body, the surface of which is composed of thin layers, which are continually changing in thickness, such as a soap-bubble, or a thin coating of tar or oil swimming on water, and which are exemplified in Newton’s rings.

As each shade of colour is an index of the temperature of the steel, and as this determines its adaptability for various purposes, all that the workman has to do, when he requires it for any special object, is to heat it by the proper methods (such as a bath of oil, or tallow, or melted metal) until it acquires the desired colour, and then to allow it to gradually cool.

The following table, exhibiting the different melting points of steel when employed in the manufacture of different kinds of works, together with the corresponding colours, the composition of the metallic baths, &c., is from Dr Wagner’s ‘Handbook of Chemical Technology,’ edited by W. Crookes, Esq., F.R.S.

Composition of
Metallic Mixture.
_____¦_____ Melting
Lead. Tin. Point. Temperature.

Lancets 7 4 220° C Hardly pale yellow.
Razors 8 4 228° ” Pale yellow to straw yellow.
Penknives 8-1/2 4 232° ” Straw yellow.
Pairs of scissors 14 4 254° ” Brown.
Clasp-knives, joiners’ and } 19 4 265° ” Purplish colour.
carpenters’ tools }
Swords, cutlasses, watch- } 48 4 288° ” Bright blue.
springs }
Stilettos, boring tools, and} 50 2 292° ” Deep blue.
fine saws }
Ordinary saws {in boiling linseed}
{oil } 316° ” Blackish blue.

Steel is of a greyish-white colour, and has a sp. gr. varying from 7·66 to 7·93. During hardening the sp. gr. becomes reduced from 7·93 to 7·66, whilst it experiences a slight increase of volume. The property (already pointed out) that steel possesses of becoming hard after being heated to redness, and suddenly chilled, does not belong to pure iron, such as may be obtained by electrolysis. Unlike pure iron, too, steel presents a granular instead of a fibrous structure when broken; the best samples closely resembling silver in this respect. The chemical difference between hard and soft steel appears to consist in the much more intimate combination of the carbon with the iron in the hard variety than in the soft. In this latter kind the carbon seems to be only mechanically mixed, for if it be immersed in hydrochloric acid the iron is dissolved, and leaves the carbon behind. Steel is the most tenacious of all the metals, being greater than that of either cast or malleable iron.

What is termed _case-hardening_ (which _see_) is a process by which small articles of iron, such as keys, gun-locks, &c., are superficially converted into steel. It is performed by heating the articles in contact with iron filings or powdered charcoal. Another method is to make the iron substance red hot, and then to sprinkle powdered potassic ferrocyanide all over it.

=STEREOCHROMY.= This is a branch of the pictorial art confined to the embellishment of walls and monuments. In the operations by which it is accomplished it will be seen that the soluble silicates (water glass) play an important part.

The foundation for the future picture or coloured design must be of some durable stone or imperishable cement. Over this is first placed a layer of lime mortar, to which is applied when it is dry and has become sufficiently hard, a solution of water glass, by which all the interstices of the mortar are filled up. Another coating of mortar made of sharp sand and a lye of chalk is next laid on, and this, after it has been carefully smoothed, properly levelled on the surface, and become quite dry, is washed over and thoroughly impregnated with water-glass solution. When this last layer has become dry it is ready to receive the painting, which must be executed in water colours. After laying on these colours may be permanently fixed by covering them with water glass. The following are the colours used:——Zinc white, chrome green, chrome oxide, cobalt green, chrome red, zinc yellow, oxide of iron, sulphide of cadmium, ultramarine, ochre, &c. Vermillion is inadmissible, since, in fixing, it turns from red to brown. Cobalt ultramarine, on the contrary, increases greatly in brilliancy upon the application of the fixing solution. Stereochromatic paintings are found to be very durable, and impervious to damp, smoke, or variations of temperature.

=STE′REOTYPE METAL.= See TYPE METAL.

=STER′LING.= The truth of the old proverb, that “all is not gold which glitters,” is often painfully experienced by the purchaser of modern jewelry. The following table will, therefore, prove highly useful to the reader in determining the value of articles in gold, provided he ascertain the ‘fineness’ of the metal, either by examination or written warranty:——

_Sterling value of Gold of different degrees of
‘Fineness,’_

Carats. Value per
Fine. oz. Troy.
£ _s._ _d._
24 _carats_ 4 4 11-1/2
23 ” 4 1 5
22 ” (_British standard_) 3 17 10-1/2
21 ” 3 14 4
20 ” 3 10 9-1/2
19 ” 3 7 3
18 ” (_lowest Hall-mark_) 3 3 8-1/2
17 ” 3 0 2
16 ” 2 16 7-1/2
15 ” 2 13 1
14 ” 2 9 6-1/2
13 ” 2 6 0
12 ” 2 2 5-1/2
11 ” 1 18 11
10 ” 1 15 4-1/2
9 ” 1 11 10
8 ” 1 8 3-1/2
7 ” 1 4 9
6 ” 1 1 2-1/2
5 ” 0 17 8
4 ” 0 14 2
3 ” 0 10 7-1/2
2 ” 0 7 1
1 ” 0 3 6

=STEREO-METAL.= A remarkable alloy recently invented by Baron de Rosthorn, of Vienna, and used in place of ordinary gun-metal. It consists of copper and spelter, with small proportions of iron and tin, and to these latter its peculiar hardness, tensile strength, and elasticity, are attributed.

=STETH′OSCOPE.= An instrument employed in auscultation. It consists of a tube (usually made of wood, sometimes of gutta percha) widening considerably at one end, and but slightly at the other. The wide end is applied to the chest or other part of the patient, the physician putting his ear at the other end; and from the sounds emitted by the heart, lungs, &c., the state of these parts is ascertained.

=STEW′ING.= A method of cooking food intermediate to frying and boiling, performed by simmering it in a saucepan or stewpan, with merely sufficient water to prevent burning, and to effect the object in view; the whole being served up to form the ‘dish.’ It is undoubtedly the most simple and economical, and, when skilfully conducted, one of those best calculated to develop the flavour and nutritious qualities of animal food. The following is one of the most popular stews:——

=Stew, Irish.= _Prep._ (Soyer.) Take about 2 lbs. of scrag or neck of mutton; divide it into ten or twelve pieces, and lay them in the pan; add 8 large potatoes and 4 onions cut into slices, season with 1-1/2 teaspoonful of pepper, and 3 do. of salt; cover all with water, put it into a slow oven, or on a stove, for two hours, then stir it all up well, and serve it up in deep dishes. If a little more water is added at the commencement, you can take out, when half done, a nice cup of broth.

=STILL.= A vessel or apparatus employed for the distillation of liquids on the large scale. The forms of stills, and the materials of which they are made, vary according to the purposes for which they are intended, some being exceedingly simple, whilst others are equally elaborate and complicated. The _engr._ represents the most common and useful apparatus of this kind, and the one almost exclusively employed in the laboratory. It is used as follows:——After the fluid and other matters (if any) are put into the still, the head is placed on and connected with the worm-tub or refrigerator, and the joints are all securely luted. For ordinary liquids, a stiff paste made with linseed meal and water, to which a little chalk may be added, answers well for this purpose. For corrosive liquids, nothing is better than elastic bands or rings interposed between the joints, which are then ‘brought home,’ as it is called, with screws or clamps. Heat is next applied, and the worm-tub is supplied with cold water in sufficient quantity to preserve its contents at a proper temperature; the application of the heat being so regulated that the liquid may drop from the end of the refrigerator quite cold and unaccompanied with vapour. For highly volatile liquids a closed receiver should be provided.

_a._ Body of still, which may be either placed in a steam jacket or in
a brick furnace.
_b._ Still head or capital.
_c._ Worm-tub.
_d._ Pewter-worm or refrigerator.
_e._ Cold-water pipe.
_f._ Waste-pipe.
_g._ Receiver.]

Of the various forms of distillatory apparatus that patented by Coffey in 1832 is the one almost universally employed in this country. It yields the strongest spirits obtainable on a large scale. Coffey’s still (of which a drawing is given on the next page) effects a great economy in the expenditure of heat, by causing the liquid to be exposed to a very extended heated service; whilst it effects the evaporation of the alcohol from the wash by passing a current of steam through it.

The wash is pumped from the ‘wash charger’ into the worm-tub, which passes from top to bottom of the rectifier. In circulating through this tube it experiences a slight elevation of temperature. Arrived at the last convolution of the tube in the rectifier, the wash passes by the tube M in at the top of the ‘analyser.’ It falls, and collects on the top shelf till this overflows, whence it falls on the second shelf, and so on to the bottom. All the time this operation is going on steam is passed up from the steam boiler through fine holes in the shelves, and through valves opening upwards. As the wash gradually descends in the analyser it becomes rapidly weaker in alcohol, partly from condensation of steam which is passed into it, and partly from loss of alcohol, either evaporated or expelled by the steam, till when it arrives at the bottom it has parted with the last traces of spirits.

At the same time the vapour, as it rises through each shelf of the analyser, becomes constantly richer in alcohol, and contains less and less water because of its condensation; it then passes from the top of the analyser in at the bottom of the lower compartment of the rectifier. Here it ascends in a similar way, bubbling through the descending wash, until it arrives at F, above which it merely circulates round the earlier windings of the wash pipe; the low temperature of which condenses the spirits; which, collecting on the shelf at F, flows off by the tube into the finished spirit condenser.

To still further effect a saving of heat, the water for supplying the boiler is made to pass through a long coil of pipe, immersed in boiling spent wash, by which means its temperature is raised before it enters the boiler.

Another variety of distillatory apparatus is that of Siemens’ (see page 1566), much employed in the distillation of brandy.

It consists of two mash stills set in a boiler, and capable of being alternately used by means of the three cocks (_a_, _b_, and _c_). L is the boiler; P one of the mash retorts; K is the low wine receiver; R the fore warmer, a reservoir in which the condensed water intended as feed water of the boiler is collected; C is the dephlegmator; B a reservoir for the vapours condensed in C.

From the dephlegmator the vapour passes to a condenser, not shown in the engraving.

The mash warmer consists of a cylindrical portion (_i i_), the lower part of which has an indentation (_c_). In the cylinder is placed a narrower portion (_o o_) of the real mash, containing a vessel, fitted with the heading tube (_f n_). The upper part of the fore warmer is fitted to the lower part by means of the flange (_h h_); _r_ is a stirring apparatus, which is frequently set in operation during the process of distillation. The vapours from the second still are carried into the depression (_c_) under the fore warmer, which, in order that the vapours may come into contact with the phlegma, is covered with a sieve.

The vapours surround the under part of the mash reservoir, and enter into the tube (_f_), through which they pass to the lower cylinder of the dephlegmator. The condensed water of the dephlegmator is conducted into the reservoir (A). The upper and under part of the fore warmer are made of cast iron, but the interior bottom and heating surfaces are made of copper. This kind of fore warmer has the advantage of uniformly distributing the heat, while it can be easily cleansed.

The dephlegmator (C) is so contrived that the rectified vapour can be conveyed to the condenser by two separate pipes placed in an opposite direction to each other, which are joined again in close proximity to the condenser.

The remainder of the details will be seen by studying the engraving.

Another distilling apparatus is that known as Derosne’s, which is an improvement upon one invented by Cellier-Blumenthal. This apparatus is only designed for the distillation of wine, and not, like the previous ones, of mash.

The engraving on page 1568 gives a representation of it.

It consists of two stills (A and A′); the first rectifier (B); the second rectificator (C); the wine warmer and dephlegmator (D); the condenser (F); the regulator (E); a contrivance for regulating the flow of the fluid wine from the cistern (G).

The still A′, which, as well as the still A, is filled with wine, acts as a steam boiler. The low wine vapours evolved come, when they have arrived in the rectifiers, in contact with an uninterrupted stream of wine, whereby dephlegmation is effected; the vapour, thus enriched in alcohol, becomes stronger in the vessel (D), and thus arrives at the cooling apparatus (F). In order that a real rectification should take place in the rectificators the stream of wine should be heated to a certain temperature, which is imparted to it by the heating of the condensed water. The steam from the still A′ is carried by means of the pipe (Z) to the bottom of the still A.

Both stills are heated by the fire of the same furnace. By means of the tube B′ the liquid contained in the still A can be run into the still A′. The first rectificator (B) containing a number of semicircular discs of unequal size, placed one above the other, and which are so fastened to a vertical centre rod that they can be easily removed and cleansed. The larger discs, perforated in the manner of sieves, are placed with their concave surfaces upwards.

In consequence of this arrangement the vapours ascending from the stills meet with large surfaces moistened with wine, which, moreover, trickles downward in the manner of a cascade from the discs, and comes, therefore, into very intimate contact with the vapours. The second rectificator (C) is fitted with six compartments; in the centre of each of the partition walls (iron or copper plates) a hole is cut, and over this hole, by means of a vertical bar, is fastened an inverted cup, which nearly reaches to the bottom of the compartment wherein it is placed. As a portion of the vapours are condensed in these compartments, the vapours are necessarily forced through a layer of low wine, and have to overcome a pressure of a column of liquid two centimètres high. The fore warmer and dephlegmator (D) is a horizontal cylinder made of copper fitted with a worm, the convolutions of which are placed vertically. The tube (M) communicates with this worm, the other end of which passes to O. A phlegma collects in the convolutions of this tube, which is richer in alcohol in the formost windings, and weaker in those more remote; this fluid, collecting in the lower part of the spirals, may be drawn off by means of small tubes, thence to be transferred, at the operator’s pleasure, either all or in part, by the aid of another tube and stopcocks, to the tube (O), or into the rectificator.

By means of the tube (L) the previously warmed wine of the dephlegmator can be run into the rectificator. The condensor (F) is a cylindrical vessel closed on all sides, and containing a worm communicating with the tube (O).

The other end of the condensing tube carries the distillate away. On the top of this portion of the apparatus the tube (K) is placed, by means of which wine is run into the dephlegmator. The cold wine flows into the cooling vessel by the tube (I).

Another variety of distillatory apparatus, invented by Langier, is that represented in the accompanying cut.

The fluid intended for distillation flows from the tube (_s_) into the funnel (_p_), thence into the vessel (A), entering its lower part, and serving to condense the alcoholic vapour. From this vessel the warmed fluid passes by means of the tube (_r_) into the lower part of the second vessel (B), where dephlegmation takes place by means of a condensing tube. From B the fluid flows through the tube (_c_) into the second still (C), which is heated by the hot gases evolved from the fire, kept burning under the first still (D); in the still (C) the fluid undergoes a rectification, and the vinasse flows by the tube (_e_) into the still (D); _m_ is the pipe for conveying the hot vapour from D into C; the tube (_b_) carries the alcoholic vapours into the dephlegmator. The tube (_d_) conveys the phlegma into the still (C); _g_ and _h_ are glass gauging-tubes for indicating the height of the fluid in the interior of the stills; the tube (_l_) conveys the uncondensed vapours from the dephlegmator into the condensing apparatus, while _i_ carries the vapours formed in the vessel (B) into the condensing apparatus.

The alcohol condensed in the cooling apparatus flows, as shown in the cut, into the vessel (_o_), provided with a hydrometer, which shows the strength of the liquid. The cooling apparatus of the vessel (B) consists of seven compartments or sections formed by wide spirals, to each of which, at its lower level, is attached a narrow tube, all of which tubes are connected to the tube (_d_), which latter conveys the condensed fluids back into the still.

A very simple form of apparatus in use is that figured below.

A is a cylinder made of cast iron or copper, in which the fluid to be distilled is heated by a spiral tube made of copper. The inlet of this tube is shown at _b_ and the outlet at _a._; c serves to carry off the vinasse; B is the dephlegmator, through which the fluid to be distilled continually flows in a downward direction, while the vapour of the low wine evolved in A ascends uninterruptedly.

The dephlegmator is so constructed as to have as large a surface and as many points of contact as possible. The vapour ascends to the reservoir (E), and passes into the rectifier (C) by the tube (F). The condensed portion returns through the tube (H) to the dephlegmator, whilst the uncondensed vapour passes on to the condenser of the vessel (D), where it becomes condensed, and is carried off through M. The liquid intended for distillation is kept in a tank (not shown in the engraving), placed above the apparatus, and is conveyed to the latter by the tube (L I), fitted with the stop-cock (K), so that the liquid arrives first in D, is next conveyed to C, thence through G into the dephlegmator, and finally into the cylinder.

Divers adaptations for heating by steam have been arranged, in a very convenient form, by Mr Coffey. His so-called ESCULAPIAN STILL affords the pharmaceutical chemist the means of conducting the processes of ebullition, distillation, evaporation, desiccation, &c., on the small scale. The following cut represents his apparatus.

For further information on the subject of stills consult ‘Ure’s Dictionary,’ ‘Illustrated Chemistry,’ and Wagner’s ‘Chemical Technology.’

=STIM′ULANTS.= _Syn._ STIMULANTIA, L. Medicines or agents which possess the power of exciting vital action. They are divided in general stimulants, or those which affect the whole system, as mercury or bark; and local or topical stimulants, or those which affect a particular organ or part only, as mustard applied as a poultice. Diffusible stimulants are general stimulants the effects of which are rapid but fugacious, as ether or alcohol. “Much discrimination and caution are required in the administration of articles of this class, because, if given when inflammation is present, they are liable to create more mischief than benefit; but they are called for when, on the decline of that condition of an organ or organs, a state of relaxation or torpidity exists. In this state of things a gentle stimulation materially assists the functions, and is productive of much benefit.”

=STINGS.= See BITES.

=STIR-ABOUT.= Thick gruel formed of oatmeal and water boiled together. When eaten with cold milk, it forms the porridge of the Scotch; and when mixed with the liquor in which meat or vegetables have been boiled, it is called beef brose, kale brose, &c.

=STOCK.= Among cooks, is condensed soup or jelly, used to make extemporaneous soup, broth, &c.

=STOM′ACH AFFEC′TIONS.= Those of a character to admit of being usefully noticed in a popular work are referred to under the heads APPETITE, DYSPEPSIA, SICKNESS, &c.

Dr Budd recommends small doses of ipecacuanha as a remedy for those cases of indigestion in which digestion is slow, and the food lies heavily on the stomach, and there is an inability for mental or bodily exertion for some time after meals. He says it should be given in the morning, fasting, and in quantity barely sufficient to occasion a slight feeling of vermiculating motion in the stomach, but without causing any sensation of pain or nausea. The dose to produce this effect varies from 1/4 to 2 gr. He thinks there is no other medicine which appears so effectual in removing the affections in question. Small doses of rhubarb, ginger, and cayenne pepper, have a similar kind of action, and may be given singly or together for the same purpose. “I generally prescribe from 1/2 to 1 gr. of ipecacuanha, in a pill, with 3 or 4 gr. of rhubarb. With many, a favourite remedy for the discomfort resulting from slow digestion is a grain of cayenne pepper, with 3 or 4 gr. of rhubarb. The best time for giving these medicines is shortly” (say 1/2 an hour) “before any meal after which a sense of oppression is usually felt.”

=STOPP′ERS=, when obstinately immoveable in bottles, are the most safely treated by patiently hitting them upwards alternately on opposite sides with a piece of wood. When this fails the part may be dipped into hot water.