240 



Dr. Andrews on the Heat developed 



34. Table VIII. — Oxide of Lead. 



35. The oxide of silver gave, with nitric acid, an increase of temperature of 

 2°.7 corresponding, when corrected, to an actual elevation of 3°.23. 



36. To render the numbers in each table strictly comparable with one 

 another, would require a minute investigation of the influence of every possible 

 source of a variation of temperature in the experiments ; such are, differences in 

 the specific heats of the solutions formed, alterations in the density of the liquids 

 after mixture, &c. However, from very dilute solutions being employed, and 

 also, from the results being identical when the strength of the solutions was 

 greatly varied (9), it is probable that the errors arising from such causes could 

 not amount, in most cases, to more than a few hundreths of a degree. Taking, 

 therefore, the results as they appear in the tables, it will be found on exami- 

 nation, that they are in accordance withLaw 1, (24). If we refer to the first, 

 second, and fourth tables, as being the most extensive, from the large number of 

 soluble compounds formed by potash, soda, and ammonia, it will be observed, 

 that the sulphuric acid developes from 0°.8 to nearly 1° more than the megn heat 

 given by the other acids, while the tartaric, citric, and succinic acids fall from 0°.4 

 to 0°.55 short of the same. A minute investigation of the influence of the disturb- 

 ing sources of heat will, no doubt, discover the cause of these discrepancies ; the 

 high numbers for sulphuric acid are probably connected with that acid's well- 

 known property of developing much heat when combined with successive atoms, 

 of water. All the other acids develope very nearly the same amount of heat in 

 combining with the same base ; the greatest divergences from the mean quan- 

 tity being in the case of potash, -\- 0°.24, and — 0°.13 ; in that of soda, -j- 0°.26, 



