Lerrs & Bhake—TZhe Carbonic Anhydride of the Atmosphere. 111 
“ Hlasiwetz' had already shown experimentally the untrust- 
worthy nature of Brunner’s method. Apart from the fact that the 
quantity of carbonic anhydride to be determined was much too 
small in proportion to the bulky absorption vessels (whose surfaces 
Hlasiwetz estimated to amount to seven square metres) so that a 
sufficiently accurate weighing was impossible unless very large 
quantities of air were employed, Hlasiwetz demonstrated that 
the method of drying the air exercised an important influence on 
the determination. The sulphuric acid of the drying apparatus 
absorbs carbonic anhydride, a fact which the two Rogers’ had 
already mentioned, and which had been traced quantitatively later 
by Setschenow.* Hlasiwetz condemned chloride of calcium after 
he had observed that silver solution is rendered turbid by air which 
had previously passed through a ten-foot tube containing it. 
Further he remarked that potash absorbs oxygen—a statement 
resting upon the authority of H. Rose. For pumice moistened 
with potash, this property was brought forward later by Reiset* 
who traced it tothe presence of manganous and ferrous compounds 
in the pumice, and also experimentally verified by Miintz and 
Aubin,’ who rejected on that account the methods involving direct 
weighing of the absorbing apparatus.’ 
Reiset,’ whose work on the amount of atmospheric carbonic 
anhydride is most important, employed a portable laboratory ~ 
containing an aspirator of 600 litres capacity, an absorbing 
apparatus, &e., which enabled him to make the determinations 
at the place where the air samples were collected. His method 
consisted in drawing the air first through a U tube contain- 
ing pumice moistened with sulphuric acid (which enabled him 
to determine the moisture), then through an absorbing appa- 
ratus containing baryta water saturated with barium carbonate. 
In his earlier experiments the absorbing apparatus consisted of a 
train of three Geissler’s potash bulbs, through which 600 litres of 
air passed in twelve hours, the completeness of the absorption being 
1 Hlasiwetz, ‘‘ Wien, Akad. Sitzber.,’’ 20 [1856], p. 189. 
2 Rogers, ‘‘ Amer. Journ. Science,”’ [2], 5 [1848], p. 114. 
3 Setschenow, ‘‘ Jahresber. f. Chem.,”’ 29 [1876], p. 46. 
4 Reiset, ‘Annales de Chimie et de Phys.,’’ [5], 26 [1882], p. 148. 
5 Miintz and Aubin, ‘‘ Annales de Chimie et de Phys.,” [5], 26 [1882], p. 228. 
6 Blochmann, Joe. cit. 7 Reiset, doc. cit. 
