344 



as carbonic acid could be determined with an accuracy of O.02 

 and 0.005 per cent., respectively. This degree of accuracy was 

 sufficient for my purposes at the time, and I think that it will 

 suffice for some time to come for determinations of COg- 

 tension in freshwaters. Generally, however, it will be of no 

 use to be able to determine the percentage of oxygen, and I 

 would therefore recommend the apparatus specially designed 

 by Haldane for the estimation of carbonic acid in air 4. Its 

 construction is very simple, the manipulations are easy when 

 no greater accuracy than 0.005 "/0 is wanted, and the apparatus 

 is of very small compass (8 X 13 X 3 inches) and weight 

 (6 pounds) thus being easily portable. 



I have found it possible to obtain by means of this 

 apparatus, which I have made use of in the majority of my 

 determinations, an accuracy of + 0,001 %, but this is extremely 

 difficult and I cannot therefore recommend the apparatus for 

 the purpose of tension-determination in seawater or for deter- 

 minations of the percentage of carbonic acid in the atmosphere. 

 I have tried to improve it by augmenting the dimensions, but 

 without success, because its principal defect lies in the pressure- 

 gauge which is not sufficiently sensitive. 



In the well-known apparatus constructed by Petterson and 

 modified by Sonden this difficulty has been completely overcome 

 by the application of a short, horizontal index of oil as pressure- 

 gauge, and the numerous analyses of atmospheric carbonic 

 acid, published by A. Palmqdist^), G. Troili-Petersson ^) and 

 others, abundantly show that an accuracy of O.ooi "/0 is easily 



*) Haldane: A rapid method of determining carbonic acid in air. Journ. 

 of Hygiene vol. 1 1901 pp. 109—114. The apparatus is manufactured 

 by Messrs. Müller, Orme and Co. 148 High Holborn, London. 



') Palmquist: Atmosferens Kolsyrehalt. Bihang Sv. Vet. Akad. Handl. 

 Bd. 18 Afd. Il N:o 2. 



') Troili-Petersson: Kohlensäuregehalt der Atmosphäre. Ibid. Bd. 23, П. 6- 



