36& Scientific Intelligence. 



■ 18. Caseous Oxide. — To obtain this substance quite pure, it is necessary, 

 after washing it well with alcohol, to treat it with animal charcoal, and 

 dissolve it several times in boiling water, from which it is separated by eva- 

 poration. In this state it is a beautiful white powder, inodorous, and of a 

 slight bitter taste. It is heavier than water, and is soluble in fourteen parts 

 of water at 22° C. On allowing the solution to evaporate spontaneously, 

 the caseous oxide crystallizes either in the form of elegant dendritic rami- 

 fications, or in rings composed of delicate acicular crystals of a silky lustre. 



The aqueous solution of caseous oxide exposed to a moderately warm 

 temperature runs easily into putrefaction. The liquid becomes turbid, de- 

 posits whitish flakes, and emits an exceedingly offensive odour, like that 

 evolved during the decomposition of the most highly azotized animal prin- 

 ciples. The product of the fermentation does not act as a ferment to 

 sugar. ^ 



The aqueous solution of pure caseous oxide yields with infusion of gall- 

 nuts a white flaky precipitate, soluble in excess of the precipitant. The 

 persulphate of iron, and muriate of lime, and baryta, occasion no change. 

 The muriate of platinum and sulphate of alumina act in a similar way, 

 proving the absence of an ammoniacal salt. The sub-acetate of lead gives 

 a white precipitate. Caseous oxide is more soluble in muriatic acid than 

 in water. Boiling alcohol, as Proust observed, takes up very little ; and 

 of that which is dissolved a part is deposited on cooling in the form of a 

 light white powder. 



The caseous oxide takes fire when strongly heated, and burns with flame 

 without leaving any residue. Heated in a glass retort, it fuses and swells 

 up at a temperature higher than 212°F. On raising the heat gradually, the 

 caseous oxide was not sublimed, but a large quantity of the carbonate and 

 hydrosulphate of ammonia was generated. At a still higher temperature, 

 a quantity of fatty matter was distilled of the consistence of suet. If, in- 

 stead of distilling the caseous oxide, a small fragment of it is placed in a 

 tube open at both ends, and suddenly heated by the blowpipe flame, it is al- 

 most entirely sublimed without change, but is easily decomposed by a re- 

 newal of the heat. 



The presence of sulphur in caseous oxide is demonstrated by the forma- 

 tion of sulphuretted hydrogen ; and it is further proved by rubbing a piece 

 of silver with it while heated, when the sulphui'et of silver is formed. 

 When decomposed by nitric acid it does not yield any oxahc acid, as Proust 

 states. M. Braconnot obtained a yellow fluid oil, and a yellowish liquid 

 of a bitter styptic taste, in which he detected ammonia and sulphuric acid, 

 but no oxalic acid. 



M. Braconnot has not made the ultimate analysis of caseous oxide ; but 

 from the facts above enumerated, it obviously possesses the characters of 

 an animal substance. He states with Proust that it contains very little 

 oxygen, and is of opinion that caseous oxide is a very improper name for it. 

 M. Braconnot considers it to be formed during the putrefaction of all ani- 

 mal matters, and proposes to call it aposepedine, from «»-o and <r«T««f»r, result 

 of putrefaction. It is also generated in some diseases ; at least Braconnot sup- 

 poses that the granular matter which M. Lassaigne, and after him M. Col- 



