130 Review of Dr. Thomson 



Dr. Thomson's 4th chapter, on the atomic weights and specific 

 gravities of chlorine and iodine, is remarkable only for dogmatical 

 pretension, and eulogiums of experiments of which he should be 

 ashamed. Thus, he refers to his specific gravity of chlorine gas, 

 given in the 16th volume of the Annals^ because he brought out 

 the number 2.5, so as to tally with Dr. Prout's theory, though 

 the gas, being saturated with humidity, should have had, experi- 

 mentally, the specific gravity of 2.4837, compared to moist air, 

 1.000. Then, indeed, the chlorine in its dry state would be to dry 

 air as 2.5 : 1.0. This trick of obtaining the atomic multiple num- 

 bers, in circumstances where they cannot be found, reminds us of 

 a star-gazer, who, furnished with a little quadrant, took it in his 

 head to verify and correct the zenith distances of the stars. Dis- 

 daining the equations for refraction, nutation, aberration, &c, he 

 contrived, however, to make his results come very near to the 

 places given by Dr. Maskelyne, and hence was looked up to by his 

 little coterie as a great astronomer. 



We shall here introduce an example of Dr. Thomson's experi- 

 mental reductions, on a very simple matter. " I find that at the 

 temperature of 69°, one cubic inch of water is capable of absorb- 

 ing 417.822 cubic inches of muriatic acid gas. The temperature 

 of the liquid augments considerably, and its volume, when cooled 

 down to the temperature of the air, is 1.3433 cubic inch. It is 

 obvious from this, that 100 grains of acid of this strength contain 

 103 cubic inches of acid gas ; and a cubic inch of this acid contains 

 311.04146 cubic inches of acid gas. Acid of this strength has a 

 specific gravity of 1.1958, and I find, by saturating it with calca- 

 reous spar, that it contains 40-39 per cent, of real acid, united 

 with 59.61 of water. In winter, 1 have obtained muriatic acid 

 of as high a specific gravity as 1.212.*" 



In this congeries of blunders, it is hard to say whether his expe- 

 riments or calculations be most in fault. 



The specific gravity of muriatic acid gas is rated by him at 

 1.28472. 



1. The weight of a cubic inch of water + 417.822 cubic inches 

 of muriatic acid gas is 252.5 gr. water + 163.72 gr. gas =s 416.22 

 gr. of liquid acid; and 416.22 : 163.72 :*. 100 : 39.53. 



Thus 100 grains of this liquid acid manifestly contain 39.33 

 grains of acid gas, and not 40.39, as he asserts. 



2. 416.22 grains of water occupy a volume = 1.6484 of a 

 cubic inch ; but he tells us that the 416.22 gr. of liquid acid have 

 a volume = 1.3433 cub. inch. Hence the specific gravity of the 



liquid acid is 1.227 = L6484 But Dr. Thomson asserts that 

 1.3433. 



it was 1.1958, an incompatibility which we leave him to reconcile. 



* Attempt. Dr. Thomson may find a manufacturer of muriatic acid in 

 Glasgow, who will supply him in winter with acid at 1.220. 



