Mr. Graham on the Heat disengaged in Combinations. 341 
Half an equivalent of the crystallized biphosphate of potash, 
or 42°68 grains, was dissolved in 1000 grains of water, with a 
fall of 1°12, which gives 2°24 for the whole equivalent. 
Fall from solution of 2HO.KO, PO, . 2°24 
A corresponding proportion of the crystallized binarseniate 
of potash, or 56°38 grains, were dissolved by 1000 grains of 
water, with a fall in one experiment of 1°°13, and in another 
of 1°18. In a third experiment the solution of a whole equi- 
valent of this salt, or 112°75 grains, was attended by a fall of 
temperature of 2°15. A greater discrepancy is observable in 
the results obtained from this than from most other salts, 
which appeared to arise from the full depression of tempera- 
ture not occurring at the moment of solution, but a small 
portion of it being produced in a gradual manner for three or 
four minutes after the solution. The mean of the three ob- 
servations gives 2:26 for the equivalent quantity of the salt. 
Fall from solution of 2HO.KO, AsO; . 2°26 
The thermal properties of these two salts are interesting in 
relation to the terchromate of potash. The latter salt contains 
14 atoms, which is also the number of atoms in both biphos- 
phate and binarseniate of potash, if the equivalents of phos- 
phorus and arsenic be supposed, like that of nitrogen, to re- 
present three atoms. 
Potash being common to the terchromate and biphosphate 
of potash, there remain, on subtracting that constituent from 
both salts, three equivalents of chromic acid equivalent in 
some sense to one equivalent of phosphoric acid together 
with two equivalents of water. This statement respecting 
phosphoric acid, recalls the view which has lately been pro- 
posed by M, Wurtz of the constitution of the hypophosphites, 
in which the two atoms of water which they all contain are 
supposed not to be basic, but to form part of the acid; a 
neutral hypophosphite being represented by RO + P O,H,0,, 
or rather by R O+ PO, H,. For we are here representing bi- 
phosphate of potash as K O + P O, H,, corresponding with 
the terchromate of potash K O + Cr; Og, in which P is equi- 
valent to Cr,, and O, + H, to O,. ‘The two atoms of water, 
however, may be replaced by a strong base in a biphosphate, 
but not in a hypophosphite. The relations of these salts 
show a progressive and imperceptible passage of the basic 
elements of a salt into constituents of its acid, and the exist- 
ence of intermediate conditions of the elements in question, 
which we may well conceive although our chemical formule 
fail to enable us to denote them; these formule being adapted 
only for the expression of the extreme conditions. 
