Progress of Foreign Science. 309 



Now, the 213.924 parts of oxide of lead contain 15.34 parts of 

 oxygen. This number, then, expresses the capacity of satura- 

 tion of the chromic acid." That is to say, that weight of every 

 base which 100 parts of chromic acid neutralize, must contain 

 15.34 parts of o.xygen. Again, from the decomposition of Si-, 

 berian chrornate of lead, he thus argues : " The loss in this ex- 

 periment can be nothing but oxygen ; so that 24.25 parts of 

 green oxide of chromium will aftbrd, with 7.37 parts of oxygen, 

 31.62 parts of chromic acid. Now, the oxygen contained in 

 the 68.38 parts of oxide of lead is 4.9, which, multiplied by 

 1|, gives a product of 7.35 ; that is to say, chromic acid, when 

 it is reduced to the state of green oxide, loses a quantity of 

 oxygen, equivalent to H times its capacity of saturation." " The 

 analysis" (of chromate of barytes) " has then given^ 



Barytes . 59.68 



Oxide of chromium . 30.43 

 Loss . 9.69 



These 59.88 parts of barytes contain 6.26 parts of oxygen, and 

 6.26x1^=9.39. The result of this analysis accords, there- 

 fore, with that of the preceding experiment (on the Siberian 

 chromate.) The small difference {z-0.3,) can be ascribed only 

 to an error of observation, inseparable from this mode of ope- 

 rating." 



Now, we must confess that, though the experiments were 

 judicious and accurate, and though the reasoning be ultimately 

 not imtrue, yet it is presented in so involved a manner as to 

 create very superfluous confusion to the reader. Instead of 

 hanging his results upon a little peg of a corollary to the sys- 

 tem of equivalents, why does he not assign them their due po-. 

 sition in the general fabric, so that we could at once see their 

 relation to every other chemical body, on the comprehensive 

 plan of Richter? Direct experiments shew that chromic acid 

 has the equivalent weight of 6.5 on the oxygen scale (or 6.54 

 by the above synthesis of the chromate of lead ;) and that it 

 contains 3 atoms of oxygen to one of metal, while its green 

 oxide seems to consist, by the preceding experiments, of 3 atoms 

 of oxygen to 2 of metal. On this point we shall say a word or 

 two in its place ; our sole object here being the general prin- 

 ciples of combination. 



M. A. le Roger et J. A. Dumas, Pharmaciens, have subjected 

 a number of bodies to a nice hydrostatic process, in order to 

 determine their speciKc gravity very exactly, and thence deduce 

 a general atomic law. They employed both alcohol and oil of 

 turpentine for the liquids of immersion. They justly observe 

 that M. Hassenfratz, by employing mercury as the iiy-.irostatic 

 liquid in the examination of salts, fell into gross errors, such as 

 that caustic lime and calcined alum were lighter than wutcr, 



