112 Scientific Proceedings, Royal Dublin Society. 
indicated by the clearness of the fluid in the end bulbs nearest to 
the aspirator. Later he employed a different form of apparatus 
consisting of a tube half a metre long and about 4 em. bore, con- 
taining three platinum plates shaped like the lid of a tin canister, _ 
but with flexible and slightly conical sides, causing them when 
pushed into the tube to retain their position; the lowest being at 
the bottom of the tube, the second at a distance of about 12 cm. 
above it, and the third at the same distance above the second. 
These plates were each perforated with 120 holes of 3 mm. diameter. 
The tube with these plates in position was let into a wide-mouthed 
bottle provided with a second tubulure, and secured to its neck 
air-tight by a rubber collar. Above, the tube was closed by a 
cork through which a narrow tube passed communicating with a 
weighed U tube filled with pumice saturated with sulphuric acid. 
Into the wide tube 300 c.c. of baryta water were placed before each 
experiment. 
The apparatus having been attached to the aspirator, air 
passed first through a weighed U tube containing pumice 
moistened with sulphuric acid, then through the second tubulure 
of the bottle containing the wide tube, and thence bubbled through 
the perforations of the platinum discs into the baryta water, 
which was thus divided into three portions, and the air very 
thoroughly washed. Finally it passed through the second drying 
tube, the increase in whose weight denoted the loss by evaporation 
of the baryta water (afterwards made good by adding distilled 
water to it). At the end of the experiment the contents of the 
wide tube were washed down into the bottle to which it was 
attached, with a known volume of distilled water—the mixture 
then syphoned off into a stoppered bottle, allowed to remain at 
rest for forty-eight hours until the barium carbonate had subsided, 
a portion then removed by means of a pipette into another bottle 
and there titrated with standard sulphuric acid (decinormal), with 
litmus as indicator. 
Mintz and Aubin,! to whom we are also indebted for most 
valuable work on atmospheric carbonic anhydride, employed an 
entirely different method from Reiset’s, the principle of which was 
to absorb the gas by a suitable medium, then to liberate it and to 
1 Mintz and Aubin, ‘‘ Annales de Chimie et de Phys.,”’ [5], 26 [1882], p. 222. 
