frothing subsides and the mixture boils clear. The contents of the copper are then boiled with open steam, and a small quantity of lye of 12° B. is run in until the soap separates in flakes and feels hard when cold. Boiling is usually continued for several hours to insure complete saponification, and it is then allowed to separate and harden. If it is transferred to the cooling-frames before this hardening and separation is completed, a mottled soap may be obtained. A solution of ferrous sulphate added at this point produces a peculiar greenish mottled appearance, becoming red on exposure to the air, characteristic of Marseilles and Castile soaps. In smooth or "cut soaps" water or thin lye is added to the contents of the copper before the soap separates finally to form the curd, and is taken up, giving a smooth yet firm surface to the soap instead of the hard granular appearance of the true curd soap.

In the "cold process" soaps, exact weights of well-refined fats and the necessary caustic soda are used and added together at once. After short standing, they are agitated in a revolving copper provided with paddles at a temperature of not over 120° F. The materials rapidly coalesce, although the reaction is only finished after some days' standing in the cooling-frames. It is obvious that in this case all the glycerin of the fats originally taken remains distributed throughout the soap. Filling and padding materials can also be added in this case, and will be held in the soap. A small quantity of cocoanut oil added to the tallow or other fat facilitates the working of this cold process.

When "red oil" or oleic acid from the stearic acid candle manufacture is used, it may be saponified either with alkali or with alkaline carbonate, although the former is preferred. The oleic acid may also be changed first into the isomeric elaidic acid by the action of nitrous acid, and a very fine soap is then obtained resembling a tallow soap.

Compact soaps may contain from 10 to 25 per cent. of water, smooth or cut soaps may contain from 25 to 45 per cent., and filled soaps from 45 to 72 per cent. of water, besides the glycerin and impurities.

2. Stearic Acid Candle Manufacture.-Where the solid fatty acids are desired for the manufacture of candles, the fats are saponified either by the "autoclave process" of Milly, in which lime and hot water, under a pressure of 8 to 10 atmospheres, are made to decompose the fats, or they are decomposed with superheated steam, either with or without the addition of sulphuric acid. In the former process the lime forms a lime soap, which is afterwards decomposed by sulphuric acid, and the free fat acids are thoroughly washed by the aid of steam. The amount of lime taken is not sufficient to completely neutralize the fatty acids, as the steam decomposes the lime soap first formed and allows the base to attack fresh quantities of the fat. In the second process, that of superheated steam, the products are obtained quite pure and free from all foreign matters. As carried out in the Wilson and Gwynne form of apparatus, it is shown in Fig. 95. The fat is first heated in a by waste heat from the superheater below, and then flows into the retort c, which must be kept at from 290° to 315° C., and for this purpose is covered in. The superheated steam at 315° C. comes into the retort by the side tube; after some 24 to 36 hours the contents of the retort are distilled off, the fatty acids con

densing first, and the watery glycerin passing on to the farther condensing vessel. In this way a very pure commercial glycerin is obtained as well as pure fatty acids. If the temperature much exceed 315° C., acrolein forms from the decomposition of the glycerin. For the extraction of the hard stearic acid the washed fatty acids are now melted and run into troughs or dishes of tin, as shown in Fig. 96. These are placed in a room at a temperature of 20° to 30° C. and kept for two or three days, to allow the palmitic and stearic acids to crystallize, when the contents are emptied into canvas or woollen bags and pressed in an hydraulic press. The liquid oleic acid runs off, and the cakes of crude stearic acid obtained are melted and again put to crystallize at a somewhat higher temperature than before. A thorough pressing will now leave the stearic acid sufficiently firm for candle-making. A little wax or paraffin is usually added to take away the very crystalline structure, which unfits stearic acid somewhat for candle-making.

3. Oleomargarine, or Artificial Butter.-When very pure fats are taken and care is exercised in the melting and rendering, it is possible to separate solid stearin by a chilling process similar to that just described for stearic acid, and obtain as a liquid product the mixture of olein and palmitin known popularly as "oleomargarine oil." This so-called "oleo oil" is then churned with about 10 per cent. of its weight of milk, with the addition of a little butter color, and the product is salted and brought into the market as oleomargarine butter. In making what is called "butterine," neutral lard is added to the oleo oil and milk before churning, and then finished as before. At times a small quantity of sesame oil or cotton-seed oil is added to soften the texture of the product.

4. Manufacture of Glycerin and Nitroglycerin.-Glycerin is obtained in connection with the saponification of fats by the autoclave process with

lime or the saponification with superheated steam. The glycerin from the lime process is obtained in a very dilute state at first, and must be concentrated. This is done by the aid of steam, at first with free access of air, and later in vacuo. The product, brought to a specific gravity of 1.22, has a brown color and is known as "raw glycerin." It is then filtered through bone-black in closed and jacketed filters, and distilled with the aid of steam. The glycerin which distils over from the saponification in the apparatus of Wilson and Gwynne, before described, is more concentrated and freer from impurities. It still requires, however, the concentration and after-distillation with steam heat.

The

FIG. 96.

Nitroglycerin is a technical product of great commercial importance, because of its large use in mining and blasting operations. It is manufactured on a large scale, but every stage of the process must be watched with the greatest care because of the extreme danger connected with its explosions. The nitrating mixture consists of 5 parts of concentrated sulphuric acid and 3 parts of nitric acid of 1.48 sp. gr. glycerin must be relatively pure, and of sp. gr. about 1.26. The acid mixture having been placed in a wooden tank lined with lead, and cooled, by coils of leaden pipe through which ice water is circulating, to 14° to 16° C., the glycerin is run in through a small pipe, or, better, in a fine spray through a metal sieve. The liquid must be kept continuously mixed during the nitration, and the temperature not allowed to rise above about 18°. If the temperature rise suddenly or continue rising, the contents of the tank must be allowed to run at once into a larger receptacle containing cold water. The nitration of 730 pounds of glycerin takes from 2 to 21⁄2 hours. When it is completed the product is run into a vessel containing water at 21°. As the nitroglycerin separates, it is then washed first with pure water, then with water containing some soda solution, and finally with strong soda solution. The yield of nitroglycerin is greater in winter than in summer, varying from 950 to 1200 pounds of nitroglycerin from 630 pounds of glycerin. The several operations of nitration, separation, and washing are all carried out in detached buildings, and, as far as possible, compressed air is used for effecting the mixing and washing.

5. The Utilization of the Drying Oils in Paints and Varnishes.—In the classification of the oils (see p. 621) the distinction was made between drying and non-drying oils. This distinction is based upon differences in chemical composition. The drying oils, like linseed oil, contain large amounts of the glyceride of linoleic acid, which differs from oleic acid chiefly in its power of absorbing oxygen and becoming resinous. This tendency is notably accelerated by boiling the oils with certain mineral compounds like litharge, manganese dioxide, and the acetates and borates of lead, manganese, and zinc. These are known therefore as "dryers" because of the drying quality they impart to the oils. This is of great importance in the manufacture of paints and varnishes. In a paint we have the finely divided color thoroughly rubbed up and incorporated with boiled linseed oil, and this is then thinned out with oil of turpentine. In varnishes we have solutions of hard resins in oil, also thinned out, if necessary, with oil of turpentine. The resins so used are amber, copal, damar, animé, etc.

Printers' ink is also a thoroughly boiled linseed oil varnish with which is incorporated the lamp-black or other color and a small quantity of soap. Oilcloth and linoleum are also products into which boiled linseed oil

enters.

VIII. AMINES AND AMIDES.

The introduction of an alcohol or basic radical into the ammonia molecule replacing one or more hydrogen atoms gives us an amine, and just as ammonia can combine with a haloid acid to form an ammonium salt, so the amine or derived ammonia can unite with the chloride, bromide, or iodide of an alcohol radical to form a derived ammonium salt in which, for instance, the four hydrogen atoms of NH4Cl may be replaced by alcohol radicals.

We may have primary, secondary, or tertiary amines, according as one, two, or three atoms of hydrogen in NH, are replaced. We may also have monamines, diamines, or triamines, according as one, two, or three molecules of ammonia are represented. Thus :

NH. CH,, methylamine, is a primary amine.

NH. (CH3)2, dimethylamine, is a secondary amine.
N(CH3)3, trimethylamine, is a tertiary amine.
(NH2)2. C2H4, ethylenediamine, is a diamine.

N(C2H). OH, tetraethyl ammonium hydrate, is a quaternary

base.

N(CH),I, tetramethyl ammonium iodide, is a quaternary salt. The amines containing the lower alcohol radicals bear a close resemblance to ammonia, being strongly basic, having an ammoniacal odor, forming white clouds with hydrochloric acid, forming salts with haloid acids, which salts unite to form crystalline double

salts with gold and platinic chlorides. The ammonium bases are solid, very hygroscopic, and exceedingly like potash in properties.

The amines are formed by acting directly upon ammonia with the halogen compound of the alcohol radical, only in this case the primary amine first formed again reacts with the haloid compound producing the secondary amine, and so on, so that the result of the reaction is usually a mixture of primary, secondary, tertiary, and even quaternary bases. The nitro-paraffins, like CH,.NO, are also reducible with nascent hydrogen to amines. This reaction has less importance here, however, than under the aromatic nitro derivatives like nitro-benzene.

1. Monamines.-Methylamine, CH,NH,, is found naturally occurring in Mercurialis annua and M. perennis, in herring brine, in the distillation products of wood, bones, and beet-root molasses, and in the products of the decomposition of morphine, codeine, kreatin, sarcosin, and glycocoll. Is most easily prepared from acetamide, caustic soda, and bromine. Colorless gas, smelling like ammonia, and at the same time with a fish-like odor; burns with a yellowish flame. Forms a crystalline hydrochlorate

and sulphate.

Dimethylamine, (CH),NH, occurs also in herring brine and is formed in the decomposition of fish. Found also in Peruvian guano and in pyroligneous acid. It results, moreover, from the decomposition of glue and yeast. Liquid boiling at 8°-9° C.

Trimethylamine, (CH),N, is found quite widely distributed, -in the leaves of Chenopodium vulvaria, in Arnica montana, in Crataegus oxyacantha, and abundantly in herring brine. Formed also in the decomposition of lecithin, protagon, neurin, and betaïn (hence in beet sugar molasses distillation), also from alkaloids like narcotine and codeine by the action of alkalies. Liquid, with a strong odor of decomposing fish, boiling at 9° C.

The isomerism of trimethylamine, (CH,),N, and propylamine, CH,NH2, has led to the erroneous use of the latter name at times. Thus, the so-called "propylamine hydrochlorate," used at one time in medicine as a remedy for rheumatic ailments, was a salt of trimethylamine.

Tetramethyl Ammonium Iodide, N(CH3),I, is obtained readily by the direct action of CH,I upon ammonia. It crystallizes in white needles or prisms, and has a bitter taste.

Tetramethyl Ammonium Hydrate, N(CH,),OH, forms fine hygroscopic needles.

Ethylamine, CH. NH2, colorless liquid, boiling at 19°, with a