Page:The American Cyclopædia (1879) Volume III.djvu/783

 CARBON BISULPHIDE CARBONIC ACID GAS 773 large tanks of zinc, and protected from evap- oration by a layer of water. The process of its manufacture is comparatively simple. Char- coal is heated to redness in a retort, and lumps of sulphur are dropped upon it; the sulphur is at once converted into vapor, and the char- coal burns in it as readily as it would in oxy- gen; the resulting compound is conducted into a condenser and run into suitable tight reser- voirs. The charcoal must be dry, to prevent the formation of hydrogen sulphide and other fetid compounds. After the liquid has been repeat- edly rectified by distillation, its odor becomes ethereal and no longer disagreeable. It is then absolutely colorless, and closely resembles al- cohol. The percentage composition of carbon disulphide is : carbon, 15'8 ; sulphur, 84'2. It is a colorless, mobile liquid, of sp. gr. 1-268, boils at 46 C. (1 14 F.), and under ordinary cir- cumstances does not freeze at 90 0. ; if, how- ever, a current of dry air be passed over its surface, producing rapid evaporation, the tem- perature sinks to 18 C., and a portion of the liquid is converted into a snowy solid. It does not combine with water, but mixes in all pro- portions with alcohol, ether, and similar hydro- carbons. It readily dissolves resins, oils, caou- tchouc, gutta percha, camphor, sulphur, phos- phorus, and iodine ; is exceedingly inflammable, and burns, with a reddish blue flame, to sul- phurous acid and carbonic acid. When mixed with oxygen or atmospheric air it forms an ex- plosive compound. It has a high refracting power = 1-645. Previous to 1850 the only technical application of carbon disulphide was for vulcanizing India rubber. It is now (1873) manufactured on an immense scale, and its uses are daily extending. It is employed to extract the fat from bones previous to their conversion into bone black ; to dissolve the oil from seeds (olive, rape, turnip, cotton, linseed) ; to remove sulphur and bitumen from a certain class of rocks ; to economize the oil contained in wool ; to manufacture pure spices ; for the purification of paraifine; for the preparation of liquid fire ; in silver plating, a few drops in the bath adding to the brilliancy of the deposit ; to destroy rats, weevils, moths, and vermin ; as a motive power in engines ; for the artificial production of cold ; combined with oxygen, to produce an intense photographic light; for prisms of spectroscopes ; to clean linen rags which have been used to wipe machinery ; for the preservation of meat ; to protect hides and furs in warm climates; to prepare sonorous wood and coal ; to extract delicate perfumes ; in the manufacture of ferrocyanide of potas- sium; in medicine, both internally and exter- nally, as a diffusible stimulant, accelerating the pulse, augmenting the animal heat, and exci- ting the secretions of the skin, kidneys, &c. ; also for rheumatism and indolent tumors. It is used both internally and externally. Some of these applications are now conducted on a large scale, especially the chemical method of extracting fat oils by carbon disulphide, instead of the rude fat-boiling process so long in use. Carbon disulphide is frequently present in small quantities in illuminating gas, and imparts to the gas a disagreeable odor. The odor of crude carbon disulphide is intensly disgusting, like that of rotten cabbages. Carbon monosulphide and carbon sesquisulphide have been prepared by chemists, but very little is known of them, and even their existence is sometimes questioned. Carbon disulphide combines with the sulphides of the alkaline metals, forming a species of salts, called sulpho-carbonates, such for in- stance as the sulpho-carbonate of potassium, KjCSs, which contains 3 atoms of sulphur in the place of the 3 atoms of oxygen in the cor- responding carbonate, KaOOs. CARBONIC ACID GAS (synon'ymes, carbon di- oxide, carbonic anhydride), a gas discovered in 1757 by Dr. Black, and called by him fixed air. He detected it in limestone and magnesia, from which he found it could be expelled by heat and the acids, and also noticed that it was pro- duced by combustion, fermentation, and respi- ration. Lavoisier demonstrated its composition synthetically by burning carbon in oxygen, and obtaining this product. It was analyzed by Smithson Tennant, by causing it, as evolved from heated limestone, to be decomposed by the vapor of phosphorus passing over it ; car- bon was deposited in a light black powder, and the oxygen combined with the phosphorus. The composition of this gas is : Carbon, 1 atom =12, or percent 27'27 . Oxygen, 2 atoms =82, " T2-73 Its chemical equivalent then = 44, and it is rep- resented by the symbol C0 a . The volume of the oxygen it contains is the same as that of the compound produced. Compared with air, its weight is as 1-529 to 1. It may be poured almost like water from one jar into another, displacing the air before mixing with it, as may be shown by its extinguishing a light placed in the lower vessel. It is without color, but has a decided sour taste, and a pungent odor. Its feeble acid reaction is shown in transiently changing litmus paper red. Flame is immediately extinguished when it is mixed with air in the proportion of 1 part to 4. Un- mixed with air, it is entirely irrespirable ; it is rejected with violent spasms of the glottis. In the atmosphere it is universally diffused in proportion exceeding 4 volumes in 10,000 by measure, even at the greatest height reached by man. It is this small quantity which fur- nishes to growing plants the carbon of their solid structures; and as the supply is dimin- ished by this enormous absorption, the com- bustion and decay of organic bodies, and the respiration of animals, ever make good the deficiency. The great weight of this gas tends to keep it in the low places where it is gen- erated, though, like other gases, it has also the tendency to mix with atmospheric air. Hence it is always prudent, before descending into badly ventilated wells, to let a candle