254 Mr. E. A. Parnell on Sulphocyanogen. 



so dense as in the former case. The length of digestion also 

 considerably affects the result; the longer it is continued 

 (within certain limits) the more complete is the action : and 

 lastly, the method of preparation of sulphocyanogen' likewise 

 influences it; while that prepared by chlorine becomes red at 

 the commencement of the action, that prepared by nitric acid 

 becomes yellow. The cause of this difference will be imme- 

 diately explained. 



Of the two substances precipitated by acids, the lemon- 

 coloured one forms by far the largest portion ; and not having 

 obtained the other pure, I have as yet paid little attention 

 to it, although it appears intimately connected with the de- 

 compositions which occur. The last is insoluble in water 

 and alcohol, while the lemon-coloured substance is soluble 

 in both these liquids, which can consequently be used to se- 

 parate them. 



I have found the following method of procedure to be the 

 most convenient. Take three parts of sulphocyanogen (that 

 prepared by nitric acid is preferable) and four of potash, or 

 one of sulphocyanogen, and 27 or 28 parts of solution of 

 caustic potash in common use (sp. gr. 1'06), keep this mix- 

 ture at a gentle heat (120) for about three hours, and then boil 

 for half an hour. It is then entirely dissolved, but on cooling 

 a small quantity of the black matter separates, which must be 

 removed by filtration. To the filtered solution add hydro- 

 chloric or dilute sulphuric acid, which throws down the mix- 

 ture in question, sometimes of a bright lemon-colour, but more 

 frequently darker. It must be collected on a filter and washed 

 with cold water until all the chloride of potassium or sulphate 

 of potash is removed. Boiling alcohol must be used to purify 

 it, as hot water dissolves too minute a portion to be conveni- 

 ently employed for this purpose : the filtered alcoholic solu- 

 tion can be distilled nearly to dryness, which gives the sub- 

 stance perfectly pure in the form of a flocculent lemon-yellow 

 crystalline powder. 



Its taste is intensely bitter and acrid, but not immediately 

 perceptible, on account of its slight solubility: it thickens the 

 saliva, and a minute portion of its dust inhaled causes sneezing. 

 One part requires rather more than one thousand of cold 

 water to effect its solution. Boiling water dissolves 2'36 per 

 cent. Cold alcohol takes up 4 per cent., boiling alcohol about 

 14- per cent. Wood spirit possesses about the same solvent 

 power on it as alcohol. 



When ignited in the air sulphur burns, and a brown sub- 

 stance remains, which is entirely dissipated by a strong red 

 heat : heated in a tube, sulphur, bisulphuret of carbon and 



