On the Capillary Eudiometric Apparatus of Bonnier 
and Mangin for the Analysis of Air in investigating 
the Gaseous Exchanges of Plants. 
BY 
D. THODAY, M.A. (Camb.), 
Lecturer in the Physiology of Plants in the University of Manchester. 
With two Figures in the Text. 
HE apparatus devised by Bonnier and Mangin for the analysis of air 
-L as described by Aubert 1 and made by M. Golaz, of Paris, has advan- 
tages which are especially valuable in investigations of the gaseous exchanges 
of plants in which determinations of the rate of absorption of oxygen as 
well as of production of carbon dioxide are desired. The volume of gas 
required for analysis is only about 0-3 c.c., so that, for instance, small plant 
organs may be enclosed in a volume of air small enough to ensure that the 
composition of the air will become measurably altered within a reasonable 
time. The other principal advantage of the apparatus is the rapidity with 
which analyses can be made with it ; an analysis and the subsequent 
washing of the apparatus need occupy less than twenty minutes. 
This apparatus has found favour in many quarters, and those who have 
used it have generally expressed themselves well satisfied with the degree 
of accuracy which they have obtained with it. 2 On close scrutiny, however, 
their results hardly justify complete satisfaction. 
All the results of analyses of atmospheric air show a deficiency of 
oxygen amounting to o- 1-0-4 or more below the correct 20-9 %. Bonnier 
and Mangin themselves 3 found 20-8 %, which agreed with Dumas’s deter- 
mination, the one then current. Curtel, using the new apparatus, 4 found, 
however, c-oo % C 0 2 and 20-59 % 0 2 , and apparently assumed this throughout 
1 Rev. gen. de Bot., iii, 1891. Earlier forms of the apparatus are described and precautions 
discussed by Bonnier and Mangin in Ann. d. sc. nat., Bot, vi, 17, 18, 19 ; vii, 2, 3. 
2 Richards: Annals of Bot., x, 1896, p. 536; Palladin : Rev. g&i. de Bot., v, 1893; 
Maige: Rev. gen. de Bot., xxi, 1909, p. 32 ; Aubert : Rev. g£n. de Bot., iv, 1892, p. 281 ; Nicolas : 
Ann. d. sc. nat, Bot., ix, 10, 1909, p. 25 ; &c. 
3 Ann. d. sc. nat., Bot, vi, 17, 1884, p. 210. 
4 Rev. gen. de Bot., ii, 1890, p. 7. 
[Annals of Botany, Vol. XXVII. No. CVII. July, 1913.] 
Q q 2 
