330 Analysis of Scientific Books. 



the precipitation of sulphur which it occasions in this gas. But 

 the sulphur will not be precipitated in an insulated form, provided 

 enough of chlorine be present. A chloride is the result. Chlorine, 

 when put in contact with carburetted hydrogen, is said to seize the 

 hydrogen, and set the carbon free. But the formation of chloride 

 of carbon renders the above test nugatory. 



On turning to their eighth chapter, on the preparation and pre- 

 servation of re-agents, we find it stated that 200 volumes of chlorine 

 are soluble in 100 of water ; and that this solution = 24° on Baume's 

 hydrometer, corresponding to the specific gravity J. 2. This is a 

 serious error. The above proportions reduced to weight arc, l68 

 chlorine to 1 of water ; so that were the total volume of the liquid 

 to remain without increase, its specific gravity would be only 

 1.006. When the water of chlorine possesses this density or one 

 greater, we may be sure that it is contaminated, probably with mu- 

 riatic acid. They say that 133 parts of muriate of soda, with 110 

 of sulphuric acid, and 100 of oxide of manganese, should afford 

 80 of chlorine. But 133 parts of salt require for decomposition 

 106of acid, leaving only four parts of acid, instead of 110, for satu- 

 rating 100 parts of peroxide of manganese. Instead, therefore, 

 of eighty parts of chlorine, from the above erroneous propor- 

 tions, little more than forty will be obtained. 



When hydrogen is disengaged from dilute sulphuric acid by the 

 agency of zinc, it is properly enough directed to be passed through 

 a solution of potash to deprive it of sulphuretted hydrogen. They 

 take no notice of Berzelius's elegant application of hydrogen gas, as 

 a test of oxygen in bodies ; nor of a similar application of chlorine 

 gas in the examination of certain ores. — See this Journal, sm. 156; 

 and xiv. 209- 



Their process for procuring iodine is good for nothing ; and 

 when they prescribe a solution of this active body in alcohol to be 

 kept as a test, they forget the production of hydriodic acid, which 

 never fails to occur. The solution in alcohol should be, therefore, 

 an extemporaneous prescription. That, or the watery solution, is a 

 very delicate test of the presence of starch in plants, or in their 

 products. A blue or purple colour is produced. 



Bright silver is recommended as the test of sulphuretted hydro- 

 gen in mineral waters. They justly observe, in describing the 

 process for obtaining the metal pure, that its precipitated chloride 

 should be mixed with caustic potash, instcacl of the alkaline car- 

 bonate, which, during the ignition, is apt to scatter the particles of 

 silver, and prevent them running together into a button at the 

 bottom of the crucible. Tin afi'ords the best criterion of a tungstatc. 

 When the metal is plunged into a solution of the salt, a blue pre- 

 cipitate falls, which has not been examined. Messrs. Payen and 

 Chevallier prescribe, after Bergman, for the analysis of cast iron, to 

 measure the bulk of hydrogen evolved during its solution in dilute 

 sulphuric acid. They affirm that one gramme of iron should yield 

 in this way 458 gramme measures of hydrogen, at 32° F. and 



