78 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Properties of Liquid Nitrogen. — Until recently it has 

 been possible to experiment with liquid and solid nitrogen only 

 upon a small scale, but since the gas is now a commercial article 

 in Germany, where it comes compressed to about 100 atmospheres 

 in a passably pure condition, H. Erdmann has taken the oppor- 

 tunity to study the liquid on a large scale. He employed a cop- 

 per cylinder of about 1^ 1. capacity which was provided with 

 a manometer and had been tested to a pressure of six atmos- 

 pheres. This was surrounded with liquid air and connected with 

 the nitrogen bomb, so that the gas could be carefully introduced. 

 The nitrogen could be condensed at an over-pressure of # 7 

 atmosphere, while the condensation went on rapidly when this 

 pressure reached 2 or 2-J- atmospheres. The liquefied nitrogen 

 was then transferred to a We inhDld -flask by means of a siphon 

 valve. After filtration through a dry folded paper the liquid 

 nitrogen was found to be a very mobile, clear, perfectly colorless 

 liquid, which is decidedly different from the bluish colored liquid 

 air. Since liquid air, even when freshly prepared, contains 50 to 



.60 per cent of oxygen, its specific gravity is so high that pieces 

 of ice float upon it. On the other hand, ice sinks in liquid 

 nitrogen, as does also solid absolute alcohol. The latter phe- 

 nomenon agrees better with the specific gravity of liquid nitrogen 

 determined by Ramsay and Drugman (0-7914 at the boiling- 

 point), than with the determination of Dewar (0*850). When 

 liquid nitrogen is poured upon a bulb filled with dry oxygen at 

 atmospheric pressure, some of the oxygen is condensed in the 

 form of bluish drops. This does not occur when liquid air is 

 used. It is suggested that the easily prepared liquid nitrogen 

 will be of service to chemists in producing somewhat lower tem- 

 peratures than those obtainable with liquid air. — JBerichte, xxxix, 

 1207. h. l. w. 



2. The Oxidation of Ammonia to Nitrates and Nitrites. — The 

 probable exhaustion in a short time of the South American 

 nitrate beds makes it important to consider other means of pro- 

 ducing nitrates and nitrites. The principal methods thus far 

 suggested are the oxidation of atmospheric nitrogen and the oxi- 

 dation of ammonia by the aid of contact substances. Since Ger- 

 many possesses cheap water power in but few places, but has an 

 abundant supply of ammonia from coal, the utilization of the 

 second process appears to be of importance in that country. 

 Schmidt and Bocker have, therefore, made some experiments 

 with the oxidation of ammonia by atmospheric oxygen, using 

 platinum and platinized asbestos as contact substances. They 

 find as an average of many experiments a yield of from 75 to 76 

 per cent of the ammonia in the form of oxides of nitrogen, and in 

 many cases a yield of over 80 per cent. It appears, however, 

 that the process for producing nitrates cannot be carried out 



