EICHARDS AND ROWE. — SPECIFIC HEATS OF LIQUIDS. 181 



lively) were carefully weighed in a weighing burette and titrated with 

 standard alkali contained in another weighing burette, the two 

 analyses giving exactly the same result, a percentage of 4.293 grams 

 of hydrobromic acid, which corresponds to a molecular concentration 

 of 100.5 molecules of water for each molecule of hydrobromic acid. 

 This solution, like all the acid solutions, was immediately placed in a 

 large bottle of resistant glass ("nonsol") and the specific heat was deter- 

 mined as rapidly as possible. It was found that neither this glass nor 

 Jena reagent glass was essentially attacked by the dilute acids during 

 the times in which they were kept therein. 



Hydriodic acid. 



The preparation of this acid in a state of purity offered considerable 

 difficulty. Three different samples of the purest commercial product 

 which was guaranteed to conform to the usual analytical standard 

 were purchased, but each contained appreciable amounts of free iodine 

 from which it could not easily be purified. 



It should be noted, however, that a small amount of iodine would 

 not have a very important effect on the specific heat, although it was 

 exceedingly important that this amount should not increase during 

 the experiment, because such an increase would superpose the heat 

 of oxidation of the acid upon the phenomena concerned with specific 

 heat. Therefore careful analyses with sodium thiosulphate were made 

 before and afterwards in order to make sure that, during the determina- 

 tion of the specific heat, no significant oxidation had occurred. This 

 was the case when the dilution of the concentrated acid was effected 

 by adding water which had been freshly distilled and cooled in an 

 atmosphere of hydrogen, the resulting solution being kept under such 

 an atmosphere protected from oxygen. During the actual measure- 

 ment of the specific heat it was not convenient to exclude air, but 

 analysis showed that the decomposition which took place during that 

 brief time was wholly negligible. 



Each of the three samples of dilute acid was analyzed as before. 

 The first was found to contain 6.635 percent of hydrogen iodide and 

 0.032 percent of iodine. The percentages in the second were 6.025 

 and 0.031 respectively. After four experiments on the specific heat 

 another portion of this sample was analyzed and found to contain 

 6.632 percent of hydrogen iodide and 0.034 percent of iodine, having 

 been essentially unchanged. The third specimen by acidimetric 

 analysis was found to contain 6.626 percent of acid and 0.040 percent 



