14 



L. F. Nilson, 



with a predominant basal endface, owing to which -the crystals assume the 

 form of slightly oblique rhombic laminae, the edges truncated by the pyra- 

 mid-faces and the obtuse angles by the endfaces. Several other combina- 

 tions were also to be observed. The salt is very soluble. 



Analyses: 



1) 0.8858 gr. salt gave 0.4708 gr. selenium or 0.6615 gr. selenious acid, 

 and 0.2573 gr- sulphate of potassium or 0.1392 gr. potash. 



2) 0.8798 gr. salt gave 0.4665 gr. selenium or 0.6555 gr. selenious acid, 

 and 0.2578 gr. sulphate of potassium or 0.1394 gr. potash. 



3) 0.8022 gr. salt, when kept over sulphuric acid for three days, only lost 

 0.0014 gr- of its weight, but, on heating at 100° during the same time, 

 parted with 0.0435 gi'- 



Represented in 100 parts: 



found calculated 



1. 2. 3. 



Potash 15.71 15.85 — V 2 K 2 47.1 15.91 



Selenious acid. . . 74.68 74.50 — 2Se0 2 222.0 74.97 



Water (loss) . . 9-61 _9 1 65 5.42 V 2 H 2 Q 27.0 9.12 



100.00 100.00 296.1 100.00 



At 100° the salt gives off 5.42 pr ct. water; this forming upwards two 

 thirds the whole amount, it seems probable that the product thus obtained, 

 being viscid and fused in heat, glazed and slightly red-coloured by 

 reduced selenium in cold, is an anhydrous salt of the formula: 



KH.0 2 .SeO 4-SeO 2 . 



In all probability, more water cannot be expelled at this temperature, 

 the loss during the last 40 hours not exceeding 0.0005 gr. It is very remar- 

 kable that neither Berzelius nor Muspratt has obtained this salt crystalli- 

 zed, though it undoubtedly most easily among all the salts of potassium 

 and without difficulty affords large crystals. Both of them also declare the 

 salt to be highly deliquescent, although it is completely permanent on ex- 

 posure to the air. It is evident that their method of preparation has not 

 given a pure product. 



