178 PROCEEDINGS OF THE AMERICAN ACADEMY. 



of heat was evoh'ed in tlie inner vessel by means of known amounts 

 of acid and alkali, and in each case the rise in temperature caused by 

 this added heat was duly read off on the thermometers. Thus with 

 the appropriate calculation, to be described later under the individual 

 experiments, the specific heats of the various solutions were determined. 



Preparation of Materials. 



The preparation of the materials needed in the experiment naturally 

 divides itself into two categories ; first, the preparation of the acirl and 

 alkali needed to evolve measured quantities of heat, and secondly, the 

 preparation of the pure solutions whose specific heats were to be 

 determined. The former of these two categories was a very simple 

 matter and may be described in a few words. 



The standard sulphuric acid to be weighed into the l)ottle within 

 the calorimeter and there neutralized, was prepared twelve liters at a 

 time from the purest obtainal)le acid and distilled water — the result- 

 ing solution being thoroughly shaken to insure complete homogeneity. 

 The concentration was determined hy titration against a carefully 

 standardized solution of sodium hydroxide, and finally the licjuid was 

 sealed by means of paraffin ir> two-liter Jena flasks. The results of the 

 experiments made with this acid solution give abundant testimony as 

 to its permanence and constant content of ionized hydrogen. That 

 the acid should undergo no change during use, the device described 

 in the earlier article (1. c.) was utilized. The determinations of the 

 strength of Lot A gave as a mean of the individual titrations the value 

 6.274 percent. This was subsequently verified by a series of gravi- 

 metric analyses, the mean of which was 0.276 percent. 



The much more concentrated alkaline solution for the innermost 

 vessel was made up in the manner previously employed, from Kahl- 

 baum's sodium hydroxide, purified by alcohol. This solution was pro- 

 tected from further contamination by carl)onate through the use of a 

 double attachment; all entering air must pass first through a tower 

 of soda lime, and further through a wash bottle which contained some 

 of the solution from the container, to prevent evaporation of the 

 standard solution into the tower. (Figure 2) An excess of the alkali 

 was always taken in each thermal experiment, sufficient to render 

 inoperative the carbonate originally present. A series of titrations 

 with a carefully standardized hydrochloric acid solution indicated a 

 total alkalinity corresponding to the concentration 27.825 percent of 



