Page:The American Cyclopædia (1879) Volume III.djvu/782

 772 CARBOXATES CARBON DISULPIIIDE CARBONATES, the combinations of carbonic acid with bases. These are very numerous, not- withstanding that the acid itself is one of the most feeble, and is easily expelled with effer- vescence by nearly all the other acids. Merely a red heat alone expels it from all the carbon- ates, except those of potassa, soda, lithia, ba- rytes, and strontia ; and the last two are de- composed by an intense white heat. In contact with charcoal heated to redness, all are decom- posed, and a metal or an oxide is produced. The carbonates of ammonia, soda, and potassa alone are readily dissolved in water ; the others are insoluble, or nearly so ; but if free carbonic acid is present, their solubility is increased. The numerous and important class of salts formed by carbonic acid have till lately been regarded as monobasic ; in which case they would contain one equivalent of the anhydride to one of the base. But in the case of the al- kalies a second equivalent of the anhydride may be combined with the metallic oxide ; thus with potash there is also a bicarbonate or acid carbonate. Owing to the existence of these salts, conjoined with a consideration of the proper- ties of many of the compounds which carbonic anhydride forms with certain organic sub- stances, the acid is now very generally regard- ed as dibasic, in which case its formula would be the double of that formerly adopted ; car- bonate of calcium would then be represented as "GsfjQ, ; carbonate of potassium as K a ; and bicarbonate or the acid carbonate of po- tassium as KH60.. The formulas of all the carbonates hitherto regarded as neutral would, upon this view, be doubled, while those of the acid carbonates and some of the double car- bonates would retain their former value un- changed. The carbonates have considerable tendency to combine with each other and form double salts, like dolomite, which is a double carbonate of calcium and magnesium (MgCa, 2CO 3 ). Among the most important carbonates are those of lime, potassa, soda, and ammonia, the last three of which will be found treated of under the names of their bases. Carbonate of lime, in its purest natural form, is the mineral calcareous spar. Chalk is also com- posed of it, and it is the principal ingredi- ent in the limestones and marbles. So abun- dantly diffused is limestone among the strata that form the crust of the earth, that it has by some been supposed to constitute about one half of their substance. It is recognized by its moderate degree of hardness, being easily scratched with a knife to a white powder, whatever the color of the stone may be, and by its effervescing with acids. Heated to red- ness, its carbonic acid gas escapes, and quick- lime remains. But it may be subjected to in- tense heat in strong close vessels, so that it may even be melted and still retain its original composition. Lainy has invented a pyrometer for the measurement of intense heat, founded upon this property of carbonate of lime to dis- sociate its carbonic acid at high temperatures, to be again absorbed on cooling, the volume of the dissociated gas being used us the measure of the heat. If M and M' represent the atom of any two metallic monads, such as potassium and sodium, the general formulas of the carbonates will be thus indicated : normal salt, MjCOs ; acid salt, MHCO 3 ; double salt, MM'C0 3. The following table exhibits the composition of im- portant carbonates, some of which will be de- scribed under their respective bases : Carbonate of potassium K,CO 8 H, ! O Carbonate of sodium Na.CO 3 10H 2 O Acid carbonate (bicarb.) of potassium KHCO S Acid carbonate (bicarb.) of soda NalICO 3 Carbonate of calcium CaCO s Carbonate of magnesium MgCO a Dolomite MgCa2CO, Baryto-calcite BaCa2CO a. CARBONDALE, a city of Luzerne co., Penn., on the Delaware and Hudson railroad, at the head of Lackawanna valley, and near the source of the Lackawanna river, 110 m. N. N. W. of Philadelphia; pop. in 1870, 6,393. The Lack- awanna valley is extremely rich in beds of coal, which in the vicinity of Carbondale are 20 ft. thick. The mines are worked by the Delaware and Hudson canal company, who take out an- nually about 900,000 tons. The coal is drawn up inclined planes by steam engines, to a height of 850 ft. ; thence it is conveyed by railroad to Honesdale; and from Honesdale, by the Del- aware and Hudson canal, to the Hudson river. The city was incorporated in 1851. It contains eight churches, a bank, a graded school, and a weekly newspaper. CARBON BISULPHIDE (synonymes, bisulphide of carbon, sulpho-carbonic -acid, sulpho-car- bonic anhydride, sulphur alcohol, carburet of sulphur), a chemical compound of much value in the arts, prepared by burning carbon in an atmosphere of sulphur, or by distilling cer- tain metallic sulphides, as pyrites, sulphide of antimony, and zinc bknde, with charcoal. It was discovered by Lampadius at Freiberg in 1796, but was not proposed for practical uses before the year 1844, when Mr. Jesse Fisher of Birmingham, England, suggested its adaptation to the extraction of oils from seeds and fatty bodies. Many tons of it are now annually manufactured, and it is fast becoming one of the most important technical products. Only two articles are involved in the manufacture of carbon disulphide, charcoal and sulphur. When we burn carbon in the air, the pro- duct is a gas, which we can with difficulty reduce to a liquid. When carbon is burned in the vapor of sulphur, a compound is obtained which condenses at once to a liquid ; the former we write CO 3, and call carbonic anhydride (carbon dioxide), and the latter CS 2, and term snlpho-carbonic anhydride (carbon disulphide). The manufacture of carbon disulphide on a large scale is attended with as much dan- ger from fire and explosion as the refining of petroleum, and it is more injurious to the health of the workmen on account of the poisonous properties of its vapor. It is usually stored in