28 
DR. ANDREWS ON THE THERMAL CHANGES 
Salts of Lead. 
Salt. 
Weight. 
Found. 
Ref. to liquid. 
Ref. to water. 
PbO . NO, 
PbO . NO, 
i(PbO . NO,) 
i(PbO.NO,) 
|(PbO.A.3HO) 
|(PbO.A.3HO) 
41-34 
41-34 
20-67 
20-67 
23-64 
23-64 
+ 2*77 
+ 2-77 
+ 1-39 
+ 1*37 
+ 1-32 
+ 1-33 
+ 2-98 
+ 298 
+ 1*49 
+ 1*47 
+ 1-42 
+ 1-43 
+ 2-83 
+ 2-83 
+ 2-90 
+ 2-86 
+ 2-77 
+ 2-80 
In the last four experiments half quantities were taken, but the results are all 
reduced to the common standard in the fifth column. After the precipitate had sub- 
sided, the clear solution above was found to be highly alkaline, capable of precipitating 
freely the salts of lead, and containing at the same time a small quantity of lead in 
solution. These facts are well known, and prove that the preceding numbers repre- 
sent only a part of the heat due to the substitution of potash for the oxide of lead. 
Their accordance shows that the salts of lead, when similarly treated with caustic 
potash, give equal quantities of heat. 
Salts of Copper. 
Salt. 
Weight. 
Found. 
Ref. to liquid. 
Ref. to water. 
CuO . S0 3 
19-90 
+ 2-86 
+ 3-08 
+ 2*97 
CuO . SO , 
19-90 
+ 2-86 
+ 3-08 
+ 2-97 
CuO . NO, . Aq 
30-53 
+ 2-86 
+ 3-08 
+ 2-97 
CuO . NO, . Aq 
30-53 
+ 2-86 
+ 3-08 
+ 2-97 
CuCl 
16-72 
+ 2-81 
+ 3-02 
+ 2-91 
CuCl 
16-72 
+ 2-84 
+ 3-05 
+ 2-94 
CuCl 
16-72 
+ 2-80 
+ 3-01 
+ 2-90 
CuO . A . HO 
24-87 
+ 3-08 
+ 3-30 
+ 3-18 
CuO . A . HO 
24-87 
+ 3-02 
+ 3-25 
+ 3-12 
CuO . A . HO 
24-87 
+ 3-06 
+ 3-29 
+ 3-16 
The sulphate and chloride were weighed in the anhydrous state. The nitrate was 
taken in the state of moist crystals, and their composition determined by calcination, 
8*73 grains yielding 2*83 grains oxide by calcination. The result with the acetate 
showing a small excess of heat, I endeavoured to discover whether it could be referred 
to some peculiarity in the precipitate, or in the composition of the salt. The preci- 
pitate obtained in the first experiment was collected and found to weigh 10*01 grains, 
or 1 per cent, more than the theoretical quantity, which, supposing an equal excess 
of caustic potash to have been present, could only have produced an error of 0°*03. 
Of the crystals employed in the last experiment, 9*40 grains being digested with nitric 
acid and afterwards calcined, yielded 3*74 grains oxide, which is exactly the theore- 
tical result. It appears, therefore, that the acetate of copper, when decomposed by 
potash, produces about y^-th more heat than the other salts of copper. 
