302 Progress of Foreign Science. 



4. On a Crystalline Matter formed in a Solution of Cyanogen. 

 By M. Vauquelin. 



A solution strongly impregnated with cyanogen, which M. Vau- 

 quelin had preserved in his laboratory during the preceding win- 

 ter, presented a new phenomenon to him, which he had not leisure 

 to examine in his first experiments. At the end of abimt four 

 months, this solution, become of a slight amber hue, deposited 

 orange-yellow crystals, the number of which increased for some 

 time. When this deposition seemed to have ceased, he examined 

 the crystals, as also the liquor which had produced them. 



The latter had an amber colour, diffused a strong smell of 

 hydrocyanic acid, was alkaline, at least it suddenly restored the 

 colour of litmus reddened by an acid. It precipitated the sul- 

 phate of iron of a bluish green, which changed instantly to blue 

 by the addition of a drop of sulphuric acid. It is not to be 

 doubted therefore from these experiments that the solution of 

 cyanogen was converted into hydrocyanate of ammonia. It 

 contained likewise carbonic acid, for it precipitated lime water. 



Let us next pass to the examination of the properties of the 

 crystals of which we have spoken, and see if by means of their 

 properties, we can come at their chemical composition. 1 . These 

 transparent crystals have an orange yellow colour, which yields 

 a lemon-coloured powder; their form is dendritic; they have no 

 marked taste or smell; they are almost insoluble in water; 

 potash ley disengages nothing from them, nor does it dissolve 

 them. The mixture of these crystals and potash gives no 

 Prussian blue with sulphate of iron. Dilute sulphuric and 

 muriatic acids make them experience no alteration. 



Placed on burning coals, they volatilize, diffusing a white 

 smoke, and a strong smell of hydrocyanate of ammonia ; leaving 

 a very small quantity of black matter, which can be nothing but 

 charcoal. 



Heated in a glass tube, closed at one end, into which he had 

 introduced a slip of paper dipped in sulphate of iron, they pre- 

 sented the following phenomena: a little moisture soon ap- 

 peared, the paper assumed a bluish colour ; then a dull white 

 matter sublimed, and there remained in the bottom of the tube 

 only some black grains. When the tube was opened, there 

 exhaled a strong odour of hydrocyanate of ammonia, and the 

 slip of paper, when dipped into a feeble acid, took a very intense 

 blue colour. 



As to the white sublimate, it had neither smell nor taste; it 

 was insoluble in water ; placed on burning coals, it was reduced 

 into smoke, having the odour of hydrocyanic acid. Its minute 

 quantity did not permit a more detailed examination, but 

 M. Vauquelin thinks it is of the same nature as the crystals, 

 minus the humidity. 



