175 
of Edinburgh, Session 1869-70. 
oxalic, acetic, &c. — disengage sensibly less heat in combining with 
the bases than the nitric, hydrochloric, and other mineral acids. 
In his first memoir (published in 1841) the author of this com- 
munication had, on the contrary, found that the oxalic acid dis- 
engages quite as much heat as the nitric and hydrochloric acids, 
when it combines with the bases, and this property of oxalic acid 
he always regarded as the key to his whole investigations on this 
subject. He therefore considered it important to institute a new 
set of experiments in order to settle the question. These experi- 
ments, which were performed with great care, and with accurate 
instruments, are fully described in the present communication. 
The results confirm the general accuracy of his original experi- 
ments of 1841. They show that oxalic acid, far from disengaging 
sensibly less heat than the hydrochloric and nitric acids in com- 
bining with the bases, actually disengages a little more heat than 
either of those acids, when it combines with potash, soda, or 
ammonia. The following extract from a table given in the pre- 
sent communication will illustrate this point : — 
Acid. 
Potash. 
Soda. 
Ammonia. 
Oxalic, 
3 o, 058 
3°;040 
2°-648 
Hydrochloric, 
3°-021 
2°-982 
2°-623 
Nitric, 
2°-993 
2°-929 
2°-566 
The original experiments of the author, according to which 
oxalic acid stands, as regards thermal action, in the same rank as 
the phosphoric, nitric, arsenic, hydrochloric, hydriodic, boracic, and 
other mineral acids (with the exception of the sulphuric acid), are 
thus completely confirmed. The new experiments also agree with 
the former ones in showing that sulphuric acid disengages about 
^th more heat, and a group of acids comprising the tartaric, citric, 
and succinic acids, about ^th less heat than the mean of the other 
acids. The results are fully discussed in the present memoir, and 
the influence of extraneous circumstances considered, which in this, 
as in other similar physical inquiries, disturb in all cases to a cer- 
tain extent, and in some cases considerably, the experimental in- 
dications, and render them only first approximations to the general 
laws they are designed to illustrate. 
