TRANSACTIONS OF THE SECTIONS. 67 
original form of the undecomposed salt, but the crystals were quite opake and 
friable, This pseudomorphic residue, when dissolved in water and the solution set 
aside to crystallize, yielded acicular crystals of bisulphate of potash and an orange- 
red salt in rhombic needles. 
This remarkable mode of decomposition can only be accounted for by supposing the 
salt to contain bisulphate of potash. The determination of the sulphuric and chromic 
acids gave numbers, which upon this view lead to the very simple formula 
KO, HO, 2S0,+ KO, 2CrQ,. 
The strangeness of such a combination (for I am not aware that any similar one 
has been observed) makes me hesitate even to suggest it as an explanation of the 
phenomena observed, especially as I have only very partially examined the subject 
as yet. 
There appears to be several other salts of the same class. I have obtained, for 
example, compounds which, upon the supposition of their being double salts of bisul- 
phate of potash, contained an amount of sulphuric acid and chromic acid respectively, 
which would lead to the formula— 
KO, HO, 280,+2(K0, CrO3) 
KO, HO, 2S0,+3(KO, CrO,). 
The formation of these salts, and indeed the action generally of oil of vitriol upon 
a solution of bichromate of potash, affords a beautiful example of the influence of mass 
upon chemical affinity. 
When the first salt was dissolved in water and the solution evaporated and set 
aside, a salt crystallized out which did not become opake in water, and which could 
be recrystallized without change. Its analysis led to the formula 
KO, SO,+3(KO, CrO,). 
By using a slight excess of bichromate of potash in preparing chromic acid by 
Fritzsche’s process, and dissolving the precipitated red acid in a small quantity of cold 
water, Reinsch obtained a yellow salt as a residue, which crystallized in broad rhombic 
needles united together in stellated masses. To this salt he assigned the formula 
KO, SO,+KO2CrO,. This salt appears to me to have been a product of the action 
of water upon one of the salts which are formed in concentrated solutions in which 
bisulphate of potash can be formed. I obtained this compound among the products 
of decomposition of one of the salts which I have suggested to contain bisulphate of 
otash. 
. I have obtained several other combinations which I have not yet examined, among 
which I may mention the following :— 
1. I added a considerable quantity of oil of vitriol to the mother-liquor from which 
the salt KO, HO, 2S0,+ KO, 2CrO, had on one occasion separated, and then evapo- 
rated it briskly and set it aside. While hot it was of a deep brown colour, and 
crusts of chromic acid formed on the side of the vessel; as it cooled, it grew turbid, 
and the colour gradually became paler and of a purer yellowish red, as if the whole 
of the free chromic acid had again entered into combination*. After a short time, 
small crystalline scales made their appearance in the liquid, having the lustre and 
very much the appearance of spangles of metallic gold. ‘They floated upon the sur- 
face of the liquid, and acting as nuclei, they shot out in fan-like masses, the borders 
of which got covered with a delicate fringe of needles of chromic acid. They arranged 
themselves on the bottom of the basin in warty masses about the size of a half-walnut. 
They were of extreme delicacy, so that the moment the vessel was disturbed they got 
detached and flouted in the liquid like scales of iodide of lead. ‘They were rapidly 
filtered through a funnel stopped with broken glass; and as they continued to dissolve 
during the filtration, they were put upon a plate of dry plaster of Paris. The dried 
residue looked very much like chromic acid, except that it had a distinct orange 
shade, and was foliated. 
2. When the mother-liquor of one of the supposed bisulphate salts was mixed with 
another portion in which the chromic acid had been reduced to the state of Cr,O, by 
alcohol, and set aside, small crystals of chrome-alum separated, but mixed with another 
* This change may be observed in all cases where sulphuric acid is mixed with bichromate 
of potash, 
5* 
