30§ Scientific Notices — Chemistry. [Oct. 



drops of sulphurous acid, and promote its evaporation by a cur- 

 rent of air ; in a short time the gas condenses in the bulb. In 

 this way I have liquefied chlorine, cyanogen, and ammonia, 

 under a pressure of some centimetres of mercury (1 centimetre 

 — *39 of an inch). These are the only gases that I have as yet 

 tried, but I have no doubt that a great many of the others may 

 be condensed, perhaps all, by combining pressure with reduction 

 of temperature, especially by employing liquefied ammonia, cya- 

 nogen, See. which, being much more volatile than sulphurous 

 acid, may produce a more considerable reduction of temperature." 

 — (Journal de Pharmacie.) 



6. Organic Analysis by Peroxide of Copper. 

 Bischof affirms that during the decomposition of vegetable 

 substances by ignition with peroxide of copper, the carbon is 

 seldom converted completely into carbonic acid ; a portion, 

 which sometimes amounts to as much as one-twelfth of the 

 whole, escaping in the state of carbonic oxide, and remaining 

 mixed with the azote. The carbon v\ as fully peroxidized only in 

 the case of a few compounds, such as tartaric acid, which con- 

 tain naturally a large proportion of oxygen. He found some 

 difficulty in detecting the presence of a small quantity of car- 

 bonic oxide in mixture with azote, but was most successful in 

 obtaining a detonation with the electric spark, when the gaseous 

 residue (after the separation of the carbonic acid) was mixed with 

 twice or thrice its volume of oxygen. The detonation was ren- 

 dered much more certain by mixing the gaseous residue with 

 one-fourth or one-half of its volume of hydrogen ; and the 

 carbonic oxide was at the same time, by a simultaneous combus- 

 tion, converted into carbonic acid. — (Schweigger's Neues Journ. 

 vol.x. p. 25.) 



We forbear entering more minutely into his experiments, as 

 he describes his process of analysis too imperfectly to enable us 

 to judge how far it may have influenced his results. There are 

 three causes, alt of which would probably contribute materially 

 to the formation of carbonic oxide, and which it would be neces- 

 sary, therefore, in a particular manner, to guard against. 1 . The 

 intermixture of the red with the black oxide of copper. This 

 might have happened in some of Bischof's experiments, as he 

 states that he occasionally used an oxide which had been pre- 

 pared by igniting precipitated copper in a muffle. 2. The 

 employment of too high a temperature. Jf the carbonic acid 

 came in contact with metallic copper strongly heated, it would, 

 not unlikely, be reduced to a lower degree of oxidation. 3. The 

 incomplete mixture of the organic substance with the oxide of 

 copper. In this case, as in the first, the carbon at the instant 

 of its disengagement would be in contact with too small a quan- 

 tity of oxide to be fully peroxidized. 



