J 822.] Analyses of Boohs. 387 



whose density, at least at all ordinary temperatures, can be 

 increased by moisture, as it is the only one whose specific gravity 

 is less than •472. The densities of all the rest are diminished 

 by moisture, and that, the more as we descend in the scale of 

 temperature ; for as we descend, their specific gravities increase, 

 and of course the differences between them and the constant 

 quantity -472. As an inference also from this result, I may 

 remark, that the rule so much insisted upon, of taking the spe- 

 cific gravities of the gases at a low temperature, is so far from, 

 being general, as to apply to hydrogen alone. In order to 

 determine the specific gravity of a gas, it is only necessary, as is 

 well known, to take the weights of equal bulks of it and atmo- 

 .spkeric air at the same temperature, the former divided by the 

 latter, giving the specific gravity required. Air, however, is 

 always impregnated with more or less moisture, and the other 

 .gases, as usually collected, are saturated with it. Unless, there- 

 fore, they be, previous to weighing, thoroughly dried, the result- 

 ing, number must be inaccurate. Dr. Thomson's mode of reduc- 

 ing the error, which consists in saturating the gas and air before 

 w^eighing them, is valuable for all the gases but hydrogen. In 

 its case, the error would be thus increased instead of diminished. 

 The following mode of eliminating the error is perfect, and suffi- 

 ciently simple. - Let the given gas and the air be both saturated 

 with moisture. Then if W = weight of moist air, and W'' = 

 weight of moist gas, c = capacity of the flask in cubic inches, 

 and h = specific gravity of steam at the common temperature 



'W' — 'SOb b c 



of the gas and air, _ will express the specific gravity of 



the gas in its dry state : 'SOS h c =■ weight in grains of a volume 

 of steam whose magnitude = c, and specific gravity = b. The 

 rationale is obvious. 



Article XIIL 

 Analyses of Books. 



The Use of the Blowpipe in Chemical Analysis, and the Examina- 

 tion of Minerals. By J. J. Berzelius, Member of the Academy 

 of Sciences at Stockholm, &c. Translated from the French of 

 M. Fresnel, by J. G. Children, FRS. L. & E. FLS. MGS. &c. 

 With a Sketch of Berzelius* s System of Mineralogy ; a Synop^ 

 tical Table of the principal Characters of the Pure Earths and 

 Metallic Oxides before the Blowpipe, and numerous Notes and 

 Additions, by the Translator. London, 1822. 



We have great satisfaction in announcing the appearance of 

 tiiis translation of Berzelius's work on the Blowpipe. When the 



2c2 



