a »tash, O(K 
Sulphate of potash, SO‘(K?), potash species of the genus sulphate. 
7 
Researches on Salts. 339 
By calcination, the crystals give off water and nitrous vapors, 
and are converted, without changing their a: into quadribasic 
subphosphate of lead, PO? (Pb*)= Peo? OQ. Cold water 
does not change them, but boiling water converts them into tri- 
basic phosphate of lead and _ nitrate of lead. 
sides the influence of m there is another element to be 
- considered in the double dedbespotition of salts, viz., temperature. 
nm mixing a solution of nitrate of copper with neutral sul- 
phate of potash, we do not observe any phenomenon at ordinary 
temperatures. But let the mixture be heated to boiling, anda _ 
green powder will be precipitated, which when washed with 
boiling water, will give the composition of the quadribasie subsul- ; 
phate of copper, i.e. of the same salt which is precipitated by s 
potash in the neutral sulphate of copper, used in excess. 
This fact is by no means isolated. It is even still more re- , 
phate of copper; sulphate of potash can therefore act on 
hold espectit the nature of acids an 
which contain hydrogen or a metal, capable of being eeckk a 
by double decomposition for another metal or for hydr 
Hence potash and sulphate of potash are two salts of t the ‘same 
cies, but belonging to different genera. 
otash species of the genus oxyd. * 
tet 
Moreover, although the subsulphate of copper is formed only 
at the temperature of boiling water, the quadribasic subchromate 
of er, of which the composition is precisely similar, even to 
the proportion of water, is produced at the pie bah Nh 
by mixing neutral chromate of potash with neutral sulphate,or 
nitrate of copper. The fact which I point out thang caul 
tions of the chromates and those of the sulphates. The a 
holds good even in the following case: if we collect the el 
green precipitate, formed by boiling a mixture of sulphate 
potash and a gece of copper, or nitrate of copper, and examin 
it under a microscope, we Shall see that it is composed of an in- 
finite number of I haa ne les, of a green so pale that singly 
— — Se 
Wels 
ee 
