654 SCIENTIFIC RECORD FOR 1885. 



is ended the evolution tube is replaced by a receiver, sulphuric acid is 

 added, and the mixture of the two acetates is distilled to collect the 

 acetic acid, which is used again. (C. E. M./rom Comptes rend., c, 1005.) 



On Potassium Chromocyanide and Hydrochromocyanio Acid (by H. 

 Moissan). — Potassium chromocyanide is obtained in several ways: By 

 the action of potassium cyanide on chromous acetate ; by calcining a 

 mixture of potassium carbonate, dried blood, and finely-pulverized 

 chromium ; by the action of potassium cyanide on chromous chloride in 

 an apparatus filled with carbon dioxide, and by the action of potassium 

 cyanide on chromous carbonate. 



Potassium chromocyanide forms fine crystals of a light yellow color, 

 which occur several centimeters in length ; it is very soluble in water, 

 insoluble in alcohol at 94°, ether and chloroform. Its specific gravity 

 equals 1-71. The salt is anhydrous. It is permanent in the air at ordi- 

 nary temperatures. In solution it does not give as a rule precipitates 

 with acid salts of the metals. With ferrous salts it yields a red precip- 

 itate ; with zinc and lead salts, a white precipitate ; with silver, bis- 

 muth, and barium salts, a yellow precipitate. Its physiological action 

 is similar to that of ferrocyanide of potassium. It has the composition 

 K^CrCya. 



If dilute sulphuric acid be added to a concentrated solution of the 

 salt, a white crystalline precipitate forms. This is the hydrochromo- 

 cyanio acid, a very unstable body, decomposed in watery solution by 

 acids. {Ann. chitn.phys. [6J, TV, 136.) 



Notes on Nitrogen Trioxide and on Nitric Oxide. — Professor Eamsay, in 

 a paper read before the chemical section of the British Association for 

 the Advancement of Science, argued against the existence of gaseous 

 nitrogen trioxide. He pointed out that the only criterion of the exist- 

 ence of this gas is the vapor density; NO2 and NO mix without change 

 in volume, and, therefore, no combination takes place. The vapor den- 

 sity of the first portion of the gas obtained by distilling liquid NzOs, 

 corresponds to that which a mixture of NjOi, NO2, and NO should have. 



At the same place Professor Dewar made remarks on the molecular 

 weight of nitric oxide. A comparison of the curve of liquefaction of 

 nitric oxide with that of methane shows the pressure to increase more 

 rapidly with the temperature in the case of nitric oxide than in other 

 gases, a fact that appears to indicate that at low temperatures the 

 molecule of nitric oxide is of greater complexity and probably exists as 

 F2O2. {Nature, xxxii, 538 and 540.) 



Reactions between Nitric Oxide and Oxygen under Varying Conditions 

 (by G. Lunge). — The experiments described lead the author to the fol- 

 lowing conclusions : 1. In the dry state, nitric acid with an excess of 

 oxygen combines to form N2O4 exclusively, or nearly so. 2. Dry nitric 

 oxide and oxygen, with an excess of the former, yield a great deal of 



