Speyers — Heat of a Change in Connection loith 



The benzamid used came from Kalilbaum and had a melting 

 pomt of 126-5° cor. which did not change on one recrystalUza- 

 tion from ethyl alcohol, so the large difference between these 

 values and the one quoted by L. and B. is unexplaiued. In 

 the case of j/>toluidin, the difference may be due air bubbles 

 witli Schroeder. 



The next thing to be determined was the heat of formation 

 of the saturated solution from solute and solvent. 



The calorimeter used is figured 

 here. The large glass beaker held 

 5 0^^ water comfortabh\ The 

 spherical portion of c held 25^"^ 

 In this was the solute, small crys- 

 tals or coarse powder. From 7 

 to 22 grams of it. The vessel h 

 held about 4^^ and contained the 

 solvent in such quantity that when 

 run into c, a fairly thick paste was 

 formed and there was no reason- 

 able doubt that the solvent became 

 saturated before the end of the 

 experiment. It was run in at the 

 proper time by raising the long 

 ground glass stopper d. From 0*7 

 to 6'T grams of solvent. The ves- 

 sel h was securely fastened by a 

 cork into the cover of the calori- 

 meter and supported c by a water- 

 tight rubber stopper. The vessel 

 c was weighed with solute in it 

 before submersion in the calori- 

 meter and afterwards when the 

 observation of the thermometer 

 was finished. The increase in 

 weight gave the quantity run in 

 from h. The solubilities being 

 the composition of the solution formed could be cal- 

 culated. The thermometer and platinum stirrer were those 

 used in an earlier investigation into the heat of formation of 

 highly dilute solutions.f" The calorimeter stood in a bright 

 tin vessel which in turn stood in another bright tin vessel sub- 

 merged to the rim in a thermostat at 22-3°rt0-l, the space 

 between being packed with cotton. 



An experiment was made to see if the large excess of solute 



* This Journal, xiv, 293 (1902). 



f Journ. Am. Cliem. Soc. xviii, 146 (1896). 



known. 



