and a peculiar Sulphate of Potash. 431 



by only 1*13 part. We may then regard the various products 

 of the operation as follows : 



2 atoms of nitric acid, combined with 

 , 3 atoms of water, and 



2 atoms of bisulphate of potash, containing 

 2 atoms of water. 

 Supposing, however, two atoms of nitre to be decomposed by 

 four atoms of sulphuric acid, the above products appear to con- 

 tain one atom too much water ; for the strongest sulphuric 

 acid consists, as is well known, of an atom of acid and one of 

 water. It will, however, be observed, that 1 made use of sul- 

 phuric acid of sp. gr. l-84'i2 ; and this, according to Dr.Ure's 

 table, with which my experiments nearly agree, consists of 

 nearly 79-1 acid, and 20"9 water. Now a compound of four 

 atoms sulphuric acid = 160, and five atoms water = 45, would 

 consist very nearly of 78-1 acid, and 21-9 water, differing only 

 one per cent from the composition of the acid which I used, as 

 inferred froni Dr. Ure's table : this circumstance will of course 

 account for the presence of the additional atom of water in the 

 products. 



To the supersulphate of potash remaining in the retort, I 

 added nearly an equal weight of water : by the application of 

 heat, the salt was readily dissolved, without ebullition, and 

 consequently, with but little diminution of the water. The 

 salt obtained by the cooling of the solution consisted of ex- 

 tremely minute filaments resembling asbestos in appearance; 

 a part of the residual solution was so retained by the capillary 

 attraction of the crystals, that it could not be separated by 

 draining, and it was necessary to absorb it by filtering paper. 



The primary form of bisulphate of potash is either a right 

 rhombic prism, or an octahedron with a rhombic base, and 

 the crystals are usually so flat as to be tabular : it appeared to 

 be improbable that the acicular crystals which I have now de- 

 scribed, should be a variety of either of the primary forms 

 above mentioned. I thought they might, however, be bisul- 

 phate of potash containing more or less than the two atoms 

 of water, which are known to exist in it in its common form. 

 To determine this point I made the following experiments : 100 

 grains of the filamentous salt, which had been dried by ex- 

 posure to the air in a moderately warm room, were dissolved 

 in water, and solution of muriate of barytcs was added as long 

 as precipitation took place; the sulphate of barytes after wash- 

 ing and igniting, taking the mean of two ex})eriments, weighed 

 154-75 grains, equivalent to 52*45 of sulphuric acid. 



To expel the water of crystallization, as well as the excess 

 of acid, 100 grains of the filamentous salt were heated to red- 

 ness 



