Chemistry and Physics. 253 



other than are those in the tneta position. (7) These rules hold 

 good only for " monochrornophoric " compounds and for such 

 " dichromophoric " ones as have equal color-groups influenced in 

 the same way by the neighboring atoms. The color of an unsym- 

 melrical diazo-compound of the type Y-A-X-A-Z is approxi- 

 mately the same as that of a mixture of the two symmetrical 

 compounds Y-A-X-A-Y and Z-A-X-A-Z. — Zeitschr. physikal. 

 Chem., ix, 109, February, 1892. G. e. b. 



5. On Free Hydroxylamine. — The assumption that hydroxyl- 

 amine is not capable of existing free, arose apparently from the 

 presence of water in the process employed. Lobry de Bruyne 

 has now succeeded in isolating it by acting on hydroxylamine 

 hydrochloride dissolved in absolute methyl alcohol, with nearly 

 the theoretical quantity of a concentrated solution of sodium 

 methoxide, at a gentle heat. The sodium chloride produced was 

 filtered off and the filtrate was distilled under a pressure of 160- 

 200 mm ; since at this reduced pressure the alcohol carried off less 

 hydroxylamine. When most of the alcohol had been thus re- 

 moved, dry ether was added. This separated the liquid into two 

 layers, the upper containing 5*5 per cent hydroxylamine, the lower 

 53 - 5 per cent. The lower layer again distilled under a pressure 

 of 165 ram until the temperature rose to 86° gave a solution con- 

 taining 70 per cent of hydroxylamine. Finally, all the solutions 

 were mixed and distilled under a pressure of 60 mm . The residue, 

 containing 80 per cent of hydroxylamine, was fractionated in 

 three portions, the last of which solidified in long needles in the 

 cold receiver. This after pressing between filter paper, contained 

 99 # 4 per cent hydroxylamine. In this form it is a hard crystalline 

 mass, very hygroscopic and fusing at about 27'5°. Sodium 

 chloride readily dissolves in it and potassium nitrate liquefies it, 

 so that it resembles water. Sodium attacks it strongly. It is 

 inodorous and somewhat denser than water. When heated rapidly 

 on platinum foil it explodes with a clear yellow flame. It is 

 scarcely soluble in chloroform, benzene, ether, ethyl acetate or 

 carbon disulphide. Exposed to the air it first liquefies and then 

 evaporates. It appears to be stable alone as well as in solution. 

 — Rec. trav. Chim., x, 100; J. Chem. /Soc., lxii, 402, April, 1892. 



G. f. b. 



7. Physical and chemical phenomena under the influence of 

 very loio temperatures. — M. Paoul Pictet states that heat-waves 

 corresponding to low temperatures traverse all bodies with hardly 

 any resistance. A test tube filled with chloroform was placed in 

 a nitrous oxide refrigerator at —120°. A thermometer in the 

 tube showed a gradual fall to — 68°*5, when crystallization com- 

 menced. On removing the test tube to a refrigerator at — 80°, 

 the temperature indicated by the thermometer fell rapidly from 

 — 68 0, 5 to —80, while the crystals formed on the walls of the 

 test tube fused and disappeared. On replacing it in the —120° 

 refrigerator, the temperature rose to — 68 0- 5, and the crystals 

 reappeared. M. Pictet explains these phenomena by supposing his 



