30 Mr. Stenhouse on a neiso Compound 



through the tubuhire of the retort, and reaching nearly to its 

 bottom. The current of chlorine is to be sent through the 

 liquid very slowly: if this is not attended to, the temperature 

 rises very high, and the gaseous chloride of cyanogen passes 

 oflP as fast as it is formed, instead of being absorbed by the 

 alcohol, and the quantity of the compound obtained is exceed- 

 intdy diminished, if indeed its formation be not wholly pre- 

 vented. When this is the case heavy muriatic aether is almost 

 the only product ; but by careful cooling and cautious evolu- 

 tion of the chlorine this result may be easily prevented. 



When the current of chlorine has been sent through for 

 some time, abundance of crystals begin to appear in the re- 

 tort, accompanied by a violent effervescence. These crystals 

 will be found to be sal-ammoniac, the quantity of which, when 

 there was not much alcohol in the retort, is so great as to 

 convert the whole into a solid mass. If the chlorine is con- 

 tinued to be sent through the liquid after the crystals of sal- 

 ammoniac have appeared, it forms abundance of the heavy 

 muriatic a;ther, which adheres tenaciously to the chlorocyanous 

 compound, and from which it can be separated only by re- 

 peatedly dissolving it in hot alcohol, and precipitating it by 

 water. If any trace of this aether remains adhering to the 

 crystals, it communicates to them its peculiar smell and greasy 

 feel, and lowers their melting point very considerably. 



If the alcoholic solution is then treated with water, the 

 sal-ammoniac is dissolved, and the cyanogen compound falls 

 in great abundance in long silver-white needles. If this is 

 done by hot water the crystals form more slowly, and become 

 therefore larger and more beautiful. When the liquid has 

 stood some time the crystals are to be collected and washed 

 upon a filter with cold distilled water, till every trace of acid 

 is removed ; they are then quite pure. The salt which 

 remains in solution after the crystallization of the cyanogen 

 compound is not corrosive sublimate, as might be expected ; 

 it is the combination of chloride of mercury and sal-ammoniac 

 usually known as the sal-d'Alembroth ; it is much more so- 

 luble than corrosive sublimate. 



I shall now describe the second method, which is much 

 more oeconomical. 



Strong hydrocyanic acid is first made in the usual way by 

 sulphuric acid and prussiate of potash. It is then to be re- 

 distilled, and to be condensed in the alcohol intended to be 

 used, until the latter is saturated with the acid. The other 

 arrangements are precisely the same as in the first process ; 

 and the too rapid evolution of chlorine, or the heating of the 

 solution, must be carefully guarded against. The chlorine is 



