LESSONS IN CHEMISTRY. 141 



raphy. There are other hyposulphites, but no hyposulphurous 

 acids have ever been isolated. 



When sulphur vapor is passed over red-hot charcoal the sul- 

 phur combines with carbon, forming carbon sulphide, formula 

 CS 2 . It is a volatile liquid of high refractive powers. It has never 

 been frozen and is used in making thermometers. It dissolves 

 crystalline sulphur, phosphorus, India rubber, fatty matters, and 

 is one of the most injurious impurities of illuminating gas. 



When hydrogen passes over heated sulphur the two elements 

 combine forming hydrogen sulphide, a colorless gas of disgusting 

 odor, whose formula is H 2 S. It occurs in some natural waters, 

 and is formed in the decomposition of some organic substances, 

 as the albumen of eggs. It is soluble in water, and is usually 

 prepared by treating sulphide of iron with diluted sulphuric 

 acid. The chemical equation is FeS+H 2 S0 4 =FeO-fH 2 S. This 

 gas acts promptly on nearly all the metals forming sulphides. 

 Nearly every sulphide has a characteristic color, so that this 

 gas is an important reagent in chemical analysis. This gas 

 becomes a liquid under a pressure of 255 pounds, and a solid 

 at -122 F. 



PHOSPHORUS combined with calcium exists in the older rocks 

 and the soils formed from them. Its compounds are abundant in 

 plants, especially in the seeds of the cereals which furnish such a 

 large portion of the food-supply of men and domestic animals. 

 Its compounds are abundant in all parts of the animal body, 

 especially in the bones, three-fifths of whose weight consists of 

 calcium phosphates. Formerly bones were the chief source of 

 phosphorus, but extensive deposits of phosphatic rocks have 

 been discovered in Florida and other localities, from which phos- 

 phorus and its compounds may be obtained. These deposits 

 are among the later rocks, and probably derive their phos- 

 phorus from decomposing animal matters, so that our supply 

 of phosphorus comes from the older rocks through the medium 

 of plants and animals. 



In the preparation of phosphorus the animal matter is dis- 

 solved out of the bones by hot water at a high pressure, and 



