400 Intelligence and Miscellaneous Articles. 



liquids after being shaken together gradually separate, and the 

 two layers of liquid are seen unchanged. By suitably changing 

 the degree of dilution of the solutions, or by altering the pro- 

 portions, any desired colour-effect can be easily obtained ; on the 

 other hand, by adding suitable materials to one or the other solu- 

 tion the duration of their mixture can be varied at will. 



To exhibit the action of a mixture of red and green colouring- 

 matters, aldehyde green in arnylic alcohol is used for one solution 

 and cobalt salt in water for the other. Of the various preparations 

 of aldehyde green, the purest should be taken, which dissolves 

 easily in amylic alcohol with a colour like that of solutions of nickel 

 salts. It is not difficult just to hit the quantities in which the mixture 

 appears of a dull white colour. Experiment shows that mixtures 

 of pigments behave like mixtures of pure spectrum colours. Mix- 

 tures of cobalt and nickel solutions can also be used to demonstrate 

 the action of complementary colours ; by the addition of ammonium 

 or sodium chloride, or other alkaline salts, to the solution of cobalt, 

 the separation of the mixed liquids, which otherwise takes place 

 slowly, can be accelerated at will. In order to get as pure a white 

 as possible, the illumination must be as intense as practicable, and 

 the experiment made in front of a dark background, care being 

 taken to avoid any white objects. 



To show the action of the mixture of blue and yellow colouring- 

 matters, a solution of phenanthrenquinone in amylic alcohol may 

 be used, which gives a yellow solution, and for blue a solution of 

 ammonio-sulphate of copper. 



For the mixture of yellow and violet the same solution can be 

 used for the yellow, and a mixture of cobalt and copper salts in 

 water for the violet, the tint being as near that of the spectrum as 

 possible. — Wiedemann's Anncden, No. 6, 1891. 



ON A REMARKABLE NEW ACID. BY TH. CURTIUS. 

 In the course of his researches on Hydrazine the author has 

 obtained an extremely interesting body, Azoimide, or hydrogen- 

 nitride, the composition of which corresponds to the formula 



N\ 

 N 3 H=|| >NH. 



In the pure concentrated state it is a colourless liquid of extremely 

 pungent odour, which boils at 37° without decomposition, and can 

 be distilled, though it sometimes explodes with great violence at a 

 much lower temperature. In an aqueous solution it behaves just 

 as a halogen acid ; like these it is monobasic, and forms salts with 

 readiness. These salts, which are nitrides, correspond exactly to 

 the chlorides. Nitrogen silver, Ag 3 N, and the mercurous salt 

 (N 3 ) 2 Hg 2 explode when heated, or by a blow, with great violence. 

 Nitrogen ammonium, N 4 H 4 =N 3 (NH 4 ), is a body which crystallizes 

 in large brilliant prisms, which can be sublimed without decom- 

 position. — ChemiscJie Berichte, vol, xxiii. p. 3023 (1890). 



