the "mother of vinegar," consists of a multitude of minute fissure ferments. The raw materials furnishing vinegar under the influence of the acetic fermentation are, first, wine; second, spirits; third, malt wort or beer; fourth, fermented fruit juices other than wine; and fifth, sugarbeets. The wines used are those of inferior vintages and such as are unfit for drinking as wine. They should not exceed 10 per cent. in alcoholic strength. The spirits used for vinegar-making must be so diluted with water and vinegar already formed that the alcoholic strength ranges between 3 and 10 per cent. The malt wort used for malt vinegar is completely fermented and then passed through a filter of wood chips into the acetifier. Cider from apples and perry from pears are about the only fruit juices besides wine fermented for the production of vinegar. Sugarbeets are used somewhat in France for vinegar-making. Three vinegar-making processes are in use with some special modifications. First, the Orleans process, in which a series of mother-casks or "acetifiers" holding from fifty to one hundred gallons are used. These are partially filled with hot vinegar, and the wine is added in successive portions, and corresponding portions siphoned off into storage-vats at intervals. The wine vinegars obtained in this way have an agreeable aroma, that made from white wines being the most esteemed. The second process is the so-called “quick-vinegar process." It is used in Germany and this country for spirit vinegar, and in England for malt vinegar. The vinegarformer is shown in Fig. 102. About a foot above the true bottom of the cask it has a false bottom perforated, as shown in the illustration. The space between the false bottom and a wooden disk set in near the top is filled with beech-wood shavings. Just under the false bottom a series of holes is bored in the side of the cask extending all the way around. The shavings are first boiled in water and dried, then soured or soaked in warm vinegar for twenty-four hours before being put in the cask. Air circulates through the space filled with the beech shavings, entering through the holes below, and escaping through the glass tubes in the wooden disk above. The weak alcoholic liquid is then allowed to slowly trickle down through the shavings. The third process is Pasteur's process, using the vinegar fungus, or "mother of vinegar" directly, and causing it to propagate in a liquid containing suitable food (phosphates of potassium, magnesium, and lime). Cider vinegar, as is well known, is the result of a spontaneous acetification. The different vinegars may contain from 31⁄2 to 6 or even 8 per per cent. of acetic acid. The other constituents vary with the different kinds of materials used in the vinegar formation. Factitious vinegars are often made from pyroligneous acid flavored with acetic ether and colored with caramel color. XI. DERIVATIVES OF CARBONIC ACID. Carbonic acid, CO(OH),, is not known in the free state, but is supposed to exist in aqueous solution in water charged with CO,. Both this anhydride and the metallic salts of carbonic acid have already been discussed under Inorganic Chemistry, but a number of organic compounds may properly be considered as derivatives of it, and will be mentioned. 1. Sulphur Derivatives of Carbonic Acid.-From the anhydride carbon dioxide we have, by replacement with sulphur, two derivatives: Carbon Oxysulphide, COS, is formed when a mixture of sulphur vapor and carbon monoxide is led through a red-hot tube, CO + S=COS; also by heating together urea and carbon disulphide, according to the reaction: CO(NH2),+CS2 = COS + NH,CNS. Very inflammable gas, of peculiar odor, burning with blue flame. Carbon Disulphide, CS, (Carbonei Disulphidum, U. S. P.), is formed by heating carbon in sulphur vapor. When pure, has but slight odor, and is a colorless, highly refractive liquid. After exposure to the light it takes a yellow color from liberation of sulphur, and develops an offensive odor. Boils at 47°, solidifies at -116°, and melts again at -110°. Easily soluble in alcohol, ether, chloroform, benzene, fixed and volatile oils; insoluble in water. Sp. gr. 1.268. Inflammable, burning with bluish flame. Is used for dissolving caoutchouc and for the extraction of fats and fatty oils from oil seeds and from bones and wool. Three thio-carbonic acids are possible, CSSH, CO SH SH Of these, it is only necessary to consider the and CS {OH last, derivatives of which possess some importance. The ethyl derivative of this acid is called SH Xanthogenic Acid, CS -The potassium salt of this acid is formed when carbon disulphide is added to alcoholic pot ash solution. This salt, CS {SK is used extensively as an antidote for the phylloxera insect in the diseases of grape-vines and in the manufacture of artificial indigo. The copper salt, known also as "cuprous xanthate," is a yellow, insoluble compound, the formation of which serves as a characteristic test for carbon disulphide. 2. Esters of Carbonic Acid.-Both the neutral ester, CO(OC,H), known as ethyl carbonate, and the acid ester, он COOCH, known as ethyl-carbonic acid, are known. The former is a neutral liquid of agreeable odor, lighter than water, and insoluble in the latter. Boils at 126°. The latter is the counterpart of ethyl-sulphuric (sulphovinic) acid, and is not known in the free state, but only in its salts. 3. Chlorides of Carbonic Acid.—From the anhydride carbon dioxide we have the derivative carbon oxychloride, COCI。. It is obtained by the direct combination of carbon monoxide and chlorine in sunlight, and also by the oxidation of chloroform by means of chromic acid. It is a colorless gas (known also as phosgene gas), condensing to a liquid below 8°, and of powerful, suffocating odor. It is employed in the preparation of salicylic acid from benzene. Chloro-carbonic Acid, COCI(OH), is the acid chloride of carbonic acid. Both the free acid and the metallic salts are unstable, and cannot be obtained. Its esters, however, can be prepared, as COCI(OC,H), which is obtained by the action of phosgene gas upon absolute alcohol. JOH 4. Amides of Carbonic Acid.-From carbonic acid we may obtain two amides, both compounds of importance, CO {NH, known as carbamic acid, and CO {NH, carbamide or urea. {NH2 Carbamic Acid, CO(NH)OH, is not known in the free state. The alkaline and alkaline earth-salts, however, are well known. The ammonium salt is recognized as present in the official Ammonii Carbonas, U. S. P. It results whenever dry carbon dioxide and ammonia gases are allowed to react on each other: CO2+2NH, CO (ONH4. When heated it loses a molecule of water, and urea is formed. The esters of carbamic acid are called Urethanes. {OCH.-This is the compound usually Ethyl-urethane, CON known under the simple name of "Urethane." It is formed by the action of an excess of alcohol upon urea nitrate in closed vessels at a temperature of 120°-130°, the products of the reaction being ammonium nitrate and ethyl urethane. It forms colorless, prismatic crystals, fusing at 47°-50°, which are almost odorless, and have a saltpetre-like taste. Soluble in water. Is used as a soporific. Chloral-urethane (or Uraline), Somnal (a solution of chloral hydrate and urethane in alcohol), and Phenyl-urethane (or Euphorine) are other preparations of the urethane class. Urea (or Carbamide), CO{NH, is found in human urine, in that of other mammalia, birds, reptiles, and fishes. A grown man produces about 30 gms. daily. It is the final decomposition product from the oxidation of the nitrogenous compounds in the organism. It is also found in the blood, serous fluids, aqueous humor, milk, and perspiration. It was the product of the first organic synthesis made by Wöhler in 1828, who, on evaporation to dryness of an aqueous solution of ammonium cyanate, obtained urea by molecular rearrangement: CNONH, CO {NI2 (NH2. It = may also be formed from ammonium carbamate, from ammonia and phosgene gas, and from cyanamide and water. It may be obtained from urine by adding nitric acid, separating the crystals of urea nitrate, and decomposing these with barium carbonate. Urea forms quadratic prisms, melting at 132°, easily soluble in water and alcohol, but not in ether or chloroform. Urea forms crystalline compounds with both bases and acids, as well as with salts. Urea is recognized by several characteristic tests. The addition of mercuric nitrate to dilute solutions containing urea causes a white precipitate of a urea-mercuric nitrate compound; if urea crystals be touched with a drop of a concentrated aqueous solution of furfurol, and then a drop of strong hydrochloric acid, a violet color passing into purplishviolet is produced. Urea may be determined quantitatively when in solution in several ways. First, by the aid of a standard solution of mercuric nitrate (1 c.c of which corresponds to o.or gm. urea). To a measured volume of the urea solution the mercuric nitrate solution is added until all the urea has been precipitated as the double salt (2CN,H2O,Hg(NO3)2,3HgO) and a slight excess of mercury is in the solution. This is recognized by addition of a drop of caustic soda, which gives a yellow precipitate when the mercury is in excess, but a white one as long as urea is present in the solution. This is known as Liebig's method. Second, to the urea solution (urine) is added sodium hypobromite, and the nitrogen evolved is collected in a suitable apparatus and measured. The reaction is: CON2H4+3NaOBr = Ng + Na2CO3 + NaBr + 2HBr + H2O. This is known as Hüfner's method. Biuret, CHEN,O,, results when urea is heated to 150°-170°, ammonia splitting off. Forms long needles, fusing at 190°. When it is dissolved in caustic soda and a little cupric sulphate is added, an onion-red to violet color is obtained, known as the "biuret reaction." This reaction is also given by peptones and by albuminoids after boiling with alkalies. Thio-urea (Sulphurea), CS {NH2, is formed from ammonium NH2 sulphocyanate by prolonged fusion, a molecular rearrangement taking place, CNS. NH4 CS(NH2)2. Heavy rhombic prisms, melting at 172°. A derivative of sulphurea has been introduced into medicine under the name of Thiosinamine (Allyl-sulphurea), CS { NH.C,H, It is prepared by the action of ammonia upon mustard oil (allyl sulphocyanate). Colorless or slightly yellowish crystals, fusing at 74°, with slight odor of leeks, easily soluble in water, alcohol, and ether. SNH2 Sucrol (or Dulcin), CO {NH.CH2OCH-This is urea in which a hydrogen atom is replaced by the p-phenetol radical (see Aromatic Compounds). This compound has been brought for-d in medicine as a substitute for "saccharin," to be used for |