570 
SECOND REPORT - 183 ^. 
altered specific gravity, after saturation with aqueous moisture. 
These expressions follow immediately from the theory of mixed 
gases and vapours. Hence if a be the experimental specific 
gravity of the gas, determined by the method of Thomson, 
the gas and the air employed being both saturated with mois¬ 
ture, 
X.P-J+-625 i- 
P p 
P~f 
P 
■625— 
p 
a , 
an equation from which we deduce 
x = a + ’625 (« — 
From this formula it is obvious, that if the experimental spe¬ 
cific gravity a be less than unity, it is greater than the truth; 
if greater than unity, it is less than the truth ; and that the 
error is greatest in the case of the gases which recede most from 
unity on either side. With hydrogen, it amounts to 5 th, and 
with chlorine to ^th of the true specific gravities of the re¬ 
spective gases, assuming for these the values assigned to them 
by Dr. Thomson. In the case of nitric oxide, however, and 
even of azote, carbonic oxide, sulphuretted hydrogen, and some 
other gases, it is so small as to be safely negligible. 
On Atomic Weights . By E. Turner, M.D., Professor of 
Chemistry in the University of London. 
The author’s attention had been principally directed to the 
atomic weights of lead, silver, chlorine, and barium; and the 
results which he had obtained convinced him of the inaccuracy 
of many of the equivalents adopted in this country. He consi¬ 
ders the equivalent of lead to be not higher than 103*6, and not 
lower than 103*4 ; that of silver to be 108, or perhaps 108*1 ; 
he agrees with Berzelius in taking 35*45 as the equivalent of 
chlorine ; and adopts 68*7 as the equivalent of barium. Some 
of his experiments induce him to admit 14 to be the equivalent 
of nitrogen, while others are more favourable to 14*1. The 
analyses of the author agree in general very closely with those 
of Berzelius. 
The author proposes to lay the details of his researches be¬ 
fore the Royal Society during the ensuing winter, and hopes in 
the intervening period to reduce some of the equivalents within 
still narrower limits. In the mean time, without denying the 
possibility of hereafter tracing some simple relation between 
the equivalents of bodies, he is convinced that the hypothesis, 
“ of all equivalents being multiples by a whole number of the 
equivalent of hydrogen,” is inconsistent with the best analysis 
which chemists at present possess. 
