Mr. Graham on the Heat disengaged in Combinations. 349 
When the corresponding salts of zine are compared, the 
same equality is not observed, but other relations appear. 
Heat of hydration. 
Zn O, SO, + KO, Ogle Baresiear se 2 agg 
it OS) Og 0ELO ts slaenahnie Panesaest j-ogBeae 
PA OSOLS drs. se-onle veROUDdD ORE 
These quantities of heat and the quantity disengaged by 
the anhydrous sulphate of zinc, have a remarkable relation 
among themselves; if they be all divided by 0°86, we have 
Ratios of heat of hydration. 
Ba, 3 On et OF es es 4°01 
ZnO, SO,4+ KO, Fo salle ehh ale: 
ee oe Sant meen Se 6°01 
The quantity of heat disengaged by the first atom of water 
on uniting with sulphate of zinc is 1°71, If it had been only 
half that quantity, or 0°:86, and had the deficient 0°86 been 
evolved by the combination of the six following atoms, in ad- 
dition to the heat they actually evolve, then the heat disen- 
gaged by the six atoms of water which unite with protohy- 
drated sulphate of zinc, and by the double sulphate of zinc 
and potash, would be the same in both salts, as it is the same 
in the two corresponding salts of magnesia. 
The heat evolved by the corresponding copper salts with 
their ratios, is as follows :— 
Heat of hydration. Ratios. 
CuO,SO;+HO .. . 993 4° 
Beare les uhh Se oa 6° 
Cu0,SO,+KO,SO, . 5°0] 6°86 
It is to be observed, however, that while the protohydrate 
of sulphate of copper combines with only four atoms of water, 
the sulphate of copper and potash combines with six atoms; 
the usual comparison cannot therefore be made between these 
two salts. 
The principal numerical results of the paper are exhibited 
in the following tables :— 
1. Heat absorbed by equivalent quantities of crystallized 
salts on dissolving in water, 
Sulphate of magnesia. . , |, 7HO  0%92 
Sulphate of zine... 4a gee gs ee 1°00 
Protosulphate of iron PELE one 1°06 
Sulphate ofcoppr . . . . . .) 5H O '>” OF67 
Sulphate of manganese . _ eee eee 0°12 
Sulphate of magnesia and potash . 6HO  9%39 
Sulphate of magnesia and ammonia . oes 2°94 
Sulphate of manganese and ammonia eee 2°24 
