Page:Proceedings of the Royal Society of London Vol 69.djvu/493

Rh temperature T" is obtained, at which the solubility of B is equal to that of A at the temperature T. In this way the solubilities of B covering the range of known solubilities of A can be calculated.

I have tested this method in the case of a considerable number of substances of very varied character and solubility, and have, in all cases, found a very satisfactory agreement between the values of the solubility as calculated by means of the above method and those deter- mined experimentally. This is readily apparent from Tables II, III, IV, and V.

In the following tables the solubilities are expressed in gramme- molecules of substance in 100 gramme-molecules of solvent (water). With regard to the solubilities of zinc chloride and bromide, and of cadmium bromide, the values obtained by li. Dietz* were employed. In the case of the other salts, the solubilities of potassium chloride and bromide were determined by de Coppet ;f those of potassium nitrate by Andrea, \ and those of the oxy-benzoic acids by Walker and Wood. The values of R, or the ratio T/T' are calculated by means of the temperatures marked with an asterisk.

Table II. ZnBr,, and ZnCl,.ILO. r = 0-00316.

Solubility observed.

Solubility of 2 calculated.

Abs. temp, for i observed.

Abs. temp. Abs. temp, fur 2 for 2 observed. calculated.

Ratio of tempera- tures.

46-9

47-2

3080

283-2 2H3 C -6

1 -086

47-4

313 0*

283 9*

1 -102

48-0

48-0

319-2

284 ."> 2^4 '4

1 -122

49-5

49-5

833-0

2H5 -7 283 -7

1 -U>5

5i>

338-0*

28ti -2*

I -181

51-5

51 -2

352 -0

^87- (5 287-3

1 -223

52-5

51 -8

3HO -7

288-4 287-8

1 -253

53-8

52-9

372 -f>

289-4 2887

1 -290

As can be seen from the above table, the solubility of the zinc bromide changes much less rapidly with the temperature than that of zinc chloride. Since the solubility curve of zinc chloride is rather steep, a comparatively small error in the temperature gives a com- paratively large error in the calculated value of the solubility. The agreement, nevertheless, between the calculated and the determined values of the solubility is very satisfactory.

stalt'; and ' Berichte D. Chem. G- ,' 1899, vol. 32, p. 90.
 * ' Wissensehaf tliche Abhandlungen der Physikalisch-techniachen Keiohaan-

t ' Ann. de Chimie ' [5], vol. 30, p. 414.

J ' Jl. Prakt. Chem.,' vol. 137, p. 474.

' Trans. Chem. Soc.,' 1898, vol. 73, p. 618.