362, Foreign Laterature and Science. 
Chlorine theory. 
M. Vogel, of Munich, treated phosphoric acid and mu 
viate of barytes separately, each in a platinum crucible, then 
they were heated together in a platinum tube, and abund- 
ance of muriatic acid gas was obtained: the same results 
were obtained with muriate of tin and muriate of manga- 
nese, and in a less degree with muriate of silver. Boracic 
acid also with the alkaline muriates gave similar results. 
These experiments are directly contrary to those of Davy 
and of Gay Lussac, and Thenard, and if correct, cannot be 
explained upon the new theory of chlorine.—Thomson’s 
Annals, Historical Sketch for 1818. 
Dr. Thomson’s method of taking the sp. gr. of the gases. 
This method is founded on the well known fact that when 
two gases are mixed their bulk does not alter. Provide a 
large flask with a stop cock ; weigh, exhaust, weigh again, 
the difference is the weight of the common air withdrawn. 
Let it be expressed by a. Then introduce the gas to be 
weighed, taking care first to exhaust the stop cocks connect- 
ed with the apparatus, the volume of the gas which enters 
will be equal to that of the air withdrawn. Now weigh the 
flask; the increase of weight above the weight of the ex- 
hausted flask is the weight of the gas introduced ; this may 
be expressed by b. The specific gravity of the gas is 
=: without any correction for volume, as affected by heat 
or pressure. 
If the gas is mixed with common air, determine the pro- 
portion, and then deduce the specific gravity of the pure 
gas by a very simple calculation. Leet 
x=specific gravity of the pure gas. 
A=the volume of air in the mixture. 
a=the sp. gr. of air. 
B=volume of pure gas present. 
co=sp. gr. of the mixed gas. Then 
(A+ Be—Aa 
x= 
B 
Thomson’s Annals, March, 1820. 
