116 Scientific Proceedings, Royal Dublin Society. 
in the filtrate and washings, with dilute suiphuric acid. (1 cc. = 
0-8 mgs. CO,.) 
These investigations of Dalton and his pupils were either 
not generally known or had been forgotten when Pettenkofer . 
published his method in 18581; and certainly he had no know- 
ledge of them; but it is clear, from what has been said, that the 
principle of his method had been anticipated. 
Pettenkofer employed glass flasks of from 3-33 litres capacity, 
which, previous to a determination, were carefully cleaned and 
dried. To fill them with the air to be examined, a special form 
of bellows was employed with a tube attached to the inlet valve ; 
the mouth of which tube was directed successively to all parts of 
the space from which the air was to be taken. From the bellows 
the air was driven through a glass tube to the bottom of the flask. 
As soon as the latter had been properly filled, it was closed by a 
rubber cap having two openings for the introduction of tubes. 
Cne of them was closed with a glass rod, the other with a kind of 
funnel tube, which entered the flask to a depth of about 2 inches. 
The upper part of the funnel-tube was a wider tube which could 
be closed by a cork. 
30 ¢.c. of clear lime-water were next introduced into the flask 
through the funnel-tube from a pipette graduated for the purpose, 
and the funnel-tube closed with a cork. The flask was then 
agitated, so that the lime-water wetted the greater part of its 
surface, and the agitation continued for eight or ten minutes. 
Finally the excess of lime-water was determined with standard 
oxalic acid (1 ¢.c.=1mg. CaO), the acid being run directly into the 
flask from a burette, and the fluid tested from time to time with 
small strips of turmeric paper fastened to a stick, and passed 
through one of the openings in the rubber cap. The final point 
of neutralization was ascertained by removing portions of the 
liquid, and allowing them to drop on to turmeric paper. 
Later Pettenkofer modified the process in some respects. A 
six-litre flask was employed instead of one of smaller capacity ; 
baryta water was used as absorbing fluid instead of lime-water ; 
and a period of two hours was allowed for absorption. After 
1 “ Abhandlungen der naturw.-tech. Commission bei der kgl. bayer. Akad. der 
Wissenschaften,”’ 2 [1858], p. 1; also, ‘‘Chem. Soc. Journ.,”’ 10 [1858], p. 292. 
