126 Review of Dr. Thomson 



the gases. But as Dr. Thomson, and some other chemists of 

 name, have propagated incorrect ideas on the subject, we felt it 

 our duty to rectify them. We shall presently apply these plain 

 enough propositions to the Doctor's new researches, when a 

 comical conflict will be seen, between experiment in masquerade, 

 and a pattern theory. In his anxiety to monopolize the honour 

 of finishing the fabric of Dr. Prout, our author has, unhappily for 

 his fame, deranged the whole edifice, and instead of fixing the 

 key-stone, has actually laboured unwittingly to displace it. 



In order to ascertain the weight of a given volume of hydrogen 

 gas, he dissolved a certain weight of zinc in dilute sulphuric acid, 

 contained in a matrass, to whose orifice there was luted a glass 

 tube, filled with dry muriate of lime. The quantity of his zinc 

 " was unluckily very much limited by the small size of the flask," 

 whence the temperature of the mixture was less uniform, and 

 the heat of the effluent moist gas proportionately uncertain ; for 

 in one experiment, it rose from 50° to 87°, and in another from 

 48° to Sl°, when the flask stood in the air. In subsequent expe- 

 riments, therefore, he surrounded the flask with water at 48°, 

 but as he did not insert the bulb of a thermometer into the ma- 

 trass, the temperature of its interior was unknown, and conse- 

 quently that of the gas disengaged. 



On repeating Dr. Thomson's experiment, we have found that 

 the interior thermometer stood very considerably above that of 

 the exterior one, whose bulb was near the vessel, or even in con- 

 tact with it ; and that, probably, the temperature of the effluent 

 gas may be estimated at about 1 1 or 1 2° above that of the water- 

 bath surrounding the flask. 



When 100 grains of zinc were dissolved, " the loss of weight 

 sustained by the flask was 3 grains, and the tube containing the 

 muriate of lime had increased in weight 0.1G3 of a grain*." 

 From former experiments, he found that 100 grains of zinc af- 

 forded, during their solution in dilute acid, 136.88 cubic inches of 

 hydrogen gas, bar. 30.1, therm. 49°. "The specific gravity of 

 vapour at 49°, under a pressure of 30.1 inches of mercury, is 

 0.00533 ; and the weight of the vapour, contained in 136.88 cubic 

 inches of moist gas, is 0.0533 X 136.88 X 0.305 gr. = 0.2225 

 grain ; but the moisture retained by the muriate of lime was only 

 0.163 gr. It is obvious from this, that the hydrogen still re- 

 tained 0.059 of a grain." 



" If from the weight lost, amounting to 3 grains, we subtract 

 this 0.059 grain for moisture, the remainder, amounting to 2.941 

 grains, gives the true weight of the hydrogen gas exhaled, sup- 

 posing it perfectly dry. Now, from the experiments related in 

 the last section, we know that the volume of this gas, under the 



* Thomson'' s Attempt, i. 69. 



