Section 80. Specific-Volume Data. 209 



80. THE SPECIFIC-VOLUME DATA. 



To change the concentration by weight to concentration by volume 

 at the temperature (t) of the measurement, the number of milli-equiva- 

 lents per kilogram of solution was multiplied by the density of the solu- 

 tion at 4 and by the ratio of the specific volume at 4 to that at t. The 

 density was taken as unity in most cases, but special values were used 

 in the case of solutions stronger than 0.04 normal.* 



Noyes and Coolidgef have found that sodium and potassium chlo- 

 rides in 0.1 normal solution have substantially the same specific-volume 

 ratio at 306, and that this specific- volume ratio differs from that of 

 water by only 1.0 per cent. Since the solutions of ammonium chloride, 

 sodium acetate, and ammonium acetate used in the present work were 

 all less than 0.03 normal at 306, it was considered unnecessary to deter- 

 mine the specific-volume ratios for them ; but these were assumed to be the 

 same as for sodium and potassium chlorides, and the deviation from the 

 ratio for pure water was assumed proportional to the concentration. At 

 18, in all cases, the specific-volume ratio for pure water, 1.0013, was used. 



For ammonium hydroxide and acetic acid, determinations of the 

 specific-volume ratio were made at the highest temperature on solutions 

 sufficiently strong to show the deviation from pure water. For correc- 

 tions at smaller concentrations, and at 218, the deviation from the ratio 

 for pure water was assumed proportional to the concentration and to the 

 temperature difference. The error introduced by this assumption can not 

 be greater than 0.1 per cent. 



The procedure for determining specific volume was the same as that 

 employed by Noyes and Coolidge. In table 72 the first column gives 

 the date; the second, the concentration in milli-equivalents per kilogram 

 of solution; the third, the weight (in vacuo) of the solution in grams; 

 the fourth, the temperature of measurement (t) ; the fifth, the volume 

 of the solution at this temperature ; the sixth, the weight of solution cor- 

 rected for vaporization into the vapor-space ; the seventh, the specific 

 volume of the solution at t ; the eighth, the specific volume corrected to 

 302 (or 306) by adding 0.0043 per degree; and the ninth, the ratio of 

 the specific volume at t to that at 4. 



*The values of the density employed are as follows : 



Ammonia 0.1 normal 0.9992 Determined by pyenometer. 



Ammonia 0.5 normal 0.9961 Lunge <? al., Landolt-Bornstein-Meyerhoffer's 



Tabellen, 329 (1905). 



Acetic acid 0.1 normal 1.0011 



Acetic acid 0.5 normal 1.0042 Reyher, ibid., p. 344. 



Ammonium chloride ....0.04 normal 1.0007 Dijken, ibid., p. 336. 



Sodium acetate 0.04 normal 1.0020 Franz, ibid., p. 335. 



Ammonium acetate 0.04 normal 1.0008 Hager, ibid., p. 320. 



fSection 12, Part II. 



