238 PERSPIRATION AND RESPIRATION. 
Pp 
During am experiment which lasted 184 minutes, 25.210 grs. of a stearine 
candle were consumed, which must generate 36.921 litres of carbonic acid. 
During the time of the experiment 4.9722 litres of air passed through the gas- 
meter. As the difference of the carbonic acid of this air and that entering the 
apparatus from without, there results, in place of the above amount, 31.623 litres 
of carbonic acid. There were still 5.922 litres of carbonic acid remaining in 
the saloon, and hence there was found 0.6 litre, or 13 per cent., as surplus. 
II. 
The experiment lasted 215 minutes; 33.776 grs. of stearine candle were con- 
sumed, which, represent 49.510 litres of carbonic acid. 58.554 litres again 
passed through the gasmeter, together with 41.690 litres of carbonic acid. 
8.019 litres of carbonic acid remained still in the saloon. There were, therefore, 
found 0.19 litre of carbonic acid, or about 0.4 per cent. too much. 
III. 
The experiment lasted 188 minutes; 27.513 grs. of stearine candle were con- 
sumed, representing 40.298 litres of carbonic acid. 50.680 litres of air passed 
through the gas-meter, together with 33.347 litres of carbonic acid ; in the saloon 
remained still 7.828 litres of carbonic acid. ‘There were found, therefore, 0.277 
litre, or 0.6 per cent. too much. 
It will be perceived that the result of the experiments agrees very nearly 
with the theory ; better, indeed, than could have been expected in view of the 
large dimensions of the apparatus and the great rarefaction of the carbonic acid. 
The accuracy is at least fully sufficient for the purpose proposed; and by other 
experiments I have been convinced that the determination of the carbonic 
acid remaining in the saloon is the main source of the slight uncertainty which 
still occurs, as this cannot be drawn off with the desirable exactness. If the 
carbonic acid remaining in the saloon amounts to more than one-fifth of the 
quantity which is contained in the current which had passed through the gas- 
meter, the uncertainty becomes very perceptible, and may amount in case‘of 
one-third and over to even seven or eight per cent. As proof of this I adduce 
still two other trials affected with this error. 
(a.) The experiment lasted 157 minutes; 21.485 grammes of stearine candle 
were consumed, answering to 31.465 litres of carbonic acid. 42.862 litres of air 
passed through the gas-meter, together with 21.56 litres of carbonic acid. In 
the saloon remained still 7.57 litres of carbonic acid, or 52 per cent. too much. 
(b.) The experiment lasted 108 minutes; 16.129 grs. of stearine candle were 
consumed, representing 23.621 litres of carbonic acid. 29.626 litres of air 
passed through the gas-meter, together with 15.02 litres of carbonic acid. In 
the saloon remained still 6.73 litres of carbonic acid. There was found, there- 
fore, 8 per cent. too little. 
Supported by these and still other experiments, I can with safety assume 
that, in an experiment of such duration, more than four-fifths of the carbonic 
acid developed passes over into the current between the saloon and the gas- 
meter; no greater uncertainty than one or at most two per cent. is to be feared. 
As in experiments with men and animals the time may be extended to 12 and 24 
hours, the hope of attaining a still greater accuracy is not unfounded. I should 
have been pleased to extend a test experiment with candles to 24 hours; the aspira- 
tors for the examination of the air, however, which are now at my disposal, per- 
form their functions only five hours without interruption, A remedy will-be 
found for the defect within a short time in a small pump apparatus, which, in 
connexion with the large suction pumps in the engine-house, will constantly 
