Page:Proceedings of the Royal Society of London Vol 69.djvu/492

472 Table I. Calculation of the Vapour Pressures of Carbon Disulphide from the Vapour Pressures of Water.

c = 0-0006568.

Ratios of

Pressures in mill.

Abs. temps, of water.

abs. temps, of CS 2 to those of

Smoothed ratios.

Re-calculated Observed abs. temps. abs. temps, of CS 2. of CSj.

H 2 0.

50

311-3

-8161

-8160

254-0

254 -05

100

324-7

-8245

-8242

267-6

267-7

150

333-1

-8301

0-8296

276-3

276-5

200 339 '6

-8339

-8338

283-2

283-2

300 348 -9

-8403

0-8400

293-1

293-2

400 356 -0

0-8418

-8449

300-8

300 -75

500 361 ' 7

-8485

-8483

306-8

306-9

600

366-5

-8517

-8519

312-2

312-15

700 370 -7

-8545

-8545

316-8

316-75

800 374 -45

-8567

0-8571

320 -9

320-8

900 377 -8

-8589

-8590

324-5

324-5

1000

380 -85

0-8612 0-8611

327 -95

328-0

1500

393-2

-8695

-8692

341-8

341-9

2000

402-5

-8753 -8757

OOi "O

352 -3

3000

416-5-

-8852 -8850

368-6

368-7

5000

435 -85

0-8987

-8978

391 -3

391 7

ties; c is a constant which may, possibly, have the value 0, but which, in all the cases I have examined, has a small positive or negative value; t′ and t are the temperatures at which one of the substances has the two values of the solubility in question. The above equation also holds no matter whether the substances are ionised or are non-ionised, or whether their heat of solution is positive or negative.

A method, which is in all points analogous to that employed by Ramsay and Young for the calculation of vapour pressures, can thus be made use of for the calculation of solubilities. In order to calculate the solubility of any substance B by means of the known values of the solubility of another substance A, one proceeds as follows: The solubility of B at any two absolute temperatures T′₁ and T′₂ is determined. On dividing these temperatures into the temperatures T₁ and T₂, at which A has the same solubility, the ratios T₁/T′ and T₂/T′₂ are obtained. These ratios are now plotted as abscissae against the corresponding temperatures of the substance A as ordinates, and a straight line drawn through the two points thus obtained. From this straight line curve, now, different ratios can be read off, and also the corresponding values of the absolute temperatures of substance A. By dividing the absolute temperature T of substance A by the corresponding value of the temperature ratio, the