74 Scientific Intelligence. 



ply by passing through it a current of air or of hydrogen previous- 

 ly cooled to a low temperature by the agency of methyl chloride. 

 The steel cylinder containing the liquid ethylene is supported 

 vertically with its orifice downward. To this a copper worm, 3 or 

 4 millimeters in diameter, is attached, and is closed at its lower 

 end by a screw plug. On cooling this worm to —70° by means 

 of methyl chloride, the ethylene contained in it has at this tempera- 

 ture only a feeble tension, and flows out when the screw plug is 

 opened, without much loss. The liquid ethylene is received in a 

 test tube of thin glass placed within a larger glass vessel contain- 

 ing dry air. It is necessary now only to accelerate its evapora- 

 tion by passing through it a rapid current of the cooled air or 

 hydrogen, in order to see oxygen compressed in a glass tube im- 

 mersed in the ethylene, condense into a clear colorless liquid hav- 

 ing a sharply defined meniscus. By means of the hydrogen ther- 

 mometer, the temperature which was thus obtained with ethylene 

 was measured and found to be —123° ; a temperature below the 

 critical point for oxygen. In this form the experiment is one well 

 suited to the lecture table. — C. H., c, 1033, April, 1885. g. f. b. 



2. On the preparation of Cyanogen in the wet way. — While 

 studying to learn the best conditions for the preparation of Bong- 

 purple, Jacquemin mixed a concentrated solution of copper sul- 

 phate with one of potassium cyanide and immediately obtained a 

 tumultuous evolution of cyanogen gas, while the temperature of 

 the liquid rose 40°. Although this fact had been already ob- 

 served, the author has succeeded by a simple modification of the 

 experiment, in making the reaction complete so as to obtain in the 

 free state all the cyanogen of the cyanide. A solution of two 

 parts copper sulphate in four of water is placed in a flask on the 

 water bath, and by means of a funnel furnished with a stopcock, 

 a concentrated solution containing one part of pure potassium 

 cyanide is allowed to enter. The reaction begins actively even at 

 the ordinary temperature, and when this diminishes, the tempera- 

 ture of the water bath is raised. In one experiment ten grams 

 pure potassium cyanide gave 850 c. c. of pure cyanogen. If com- 

 mercial cyanide be used carbon dioxide gas is obtained in addi- 

 tion. In the reaction, cupric cyanide is at first formed. This be- 

 ing unstable separates into cuprous cyanide and cyanogen. Two 

 processes have been devised by the author for obtaining the 

 cyanogen from the cuprous cyanide. On standing, the cuprous 

 cyanide settles to the bottom of the flask and the supernatant 

 liquid is decanted. In the first process, a slight excess of a 30° 

 solution of ferric chloride is poured into the flask. The action be- 

 gins even in the cold and an abundant evolution of cyanogen 

 takes place on slightly warming the liquid. The ferric chloride 

 is reduced to ferrous chloride the excess of chlorine uniting with 

 the copper of the cuprous cyanide, producing cuprous chloride and 

 setting the cyanogen free. By the further action of the ferric 

 chloride the cuprous chloride is converted into cupric chloride. 

 The second process consists in adding to the washed cuprous 



