Chemistry and Physics. 155 



C,H 6 CO N II + (NaOH), = C,H 6 COO Na + NaN II 



By the action of an acid upon this, hydrogen azoimide HN II or 



hydrazoic acid (stickstoff-wasserstoffsaure) results. The action of 

 sodium nitrite upon» hippuryl diamide gives nitroso-hippuryl dia- 

 mide; and this on boiling with acids or alkalies gives hippuric 

 and hydrazoic acids. The new substance hydrazoic acid, is a gas 

 having a peculiar and intensely pungent odor, producing even 

 when dilute, pain in the head and dizziness, and causing inflam- 

 mation of the mucous membrane of the air passages. In aqueous 

 solution it corrodes the skin. It is a strong monobasic acid 

 recalling closely hydrochloric acid. It is readily soluble in 

 water; and on heating the solution, gas at first escapes and then 

 a concentrated aqueous acid distills over between 90° and 100°, 

 containing 27 per cent of HN 3 . This aqueous acid has the odor 

 of the gas, reddens litmus paper strongly and produces white 

 fumes with ammonia. A seven per cent solution dissolves iron, 

 zinc, copper, aluminum and magnesium with active evolution of 

 hydrogen ; and the concentrated acid appears even to attack 

 gold and silver, since it is colored red in contact with these 

 metals. Silver nitrate and mercurous nitrate give precipitates 

 of silver and mercurous nitride, AgN s and Hg 2 (N 3 ) 2 . Both the 

 acid and its salts are fearfully explosive; two c. c. of a 27 per 

 cent acid detonated with great force while being sealed and blew 

 the tube to dust. — Ber. Berl. Chem. Ges., xxiii, 3023, Oct., 1890. 



G. F. B. 



8. New Method of obtaining the Compressibility and Dilata- 

 tion of Gases. — E. H. Amagat describes an apparatus by means 

 of which he has been able to study this subject up to the tem- 

 perature of 200° C. and to a superior limit of pressure equal to 

 100 atmospheres. Results are given for oxygen, hydrogen, ozone 

 and air. The coefficient of dilatation for hydrogen diminishes 

 regularly when the pressure increases. For ozone, oxygen and 

 air, it passes through a maximum which, at the limit, corres- 

 ponds to the pressure for which the pressure multiplied by the 

 volume is a minimum. 



For hydrogen the values of ■—- are sensibly independent of the 



temperature. Air and ozone approximate to the behavior of hydro- 

 gen. This latter gas appears to attain a limiting state, towards 

 which the other gases converge when the temperature rises. 

 Forms of the isothermals are referred to in this paper. — Comptes 

 Rendus, p. 871, Dec. 8, 1890. j. t. 



9. Mechanical equivalent of heat by method of heat radia- 

 tion. — J. Sahulk^ has modified the ordinary lecture-room ap- 

 paratus by means of which the heat developed by friction is 

 shown, so that it can afford quantitative results. A revolving 



