4 lO Mr. Coathupe's Experiments on the Products 



per cent, of carbonic acid gas. The maximum observed at 

 any single examination was 7*98 per cent. It was at 8 a.m. 

 February 5th. The ?)iinimum observed at any single exami- 

 nation was 1*91 per cent. It was at 7| p.m. February 7th. 



C. T. C, February 14th, 1839. 



Having referred to some very interesting experiments made 

 by Messrs. Allen and Pepys at the laboratory of the Royal 

 Institution, and recorded in the " Philosophical Transactions 

 of the Royal Society," published in the year 1809, I was much 

 astonished to find results differing widely from my own ; and 

 therefore, with a view to ascertain the cause of these differ- 

 ences, I tested my own results by a few collateral experi- 

 ments, which were as follows : 



Feb. 18. Air respired into a bag at 8 a.m. 



No. 1. 121-25 parts became 117. .'. loss =3'51\ft't3 



No. 2. 89-25 do. do. 86. .*. do. 3-64/ S ^ 



2)7-15 



.•. average loss = 3-57 p. cent, 



which, corrected for tension, will be 3*68 per cent. 

 32 parts of the residual air from No. 1. experiment, after the 

 abstraction of the cai'bonic acid gas by lime-water, were 

 mixed with 13 parts of dry hydrogen gas received over mer- 

 cury. The eudiometer contained 45 parts, the interior and 

 exterior surfaces of the mercury being adjusted to the same 

 level. 



The thermometer stood at 47° Fahrenheit. The barome- 

 ter at 29*5 in. a Dobereiner's ball of spongy platina was in- 

 troduced into the mixture, and it absorbed 16*75 parts. 



Therefore the 32 parts of residual air contained 5*58 parts 

 of oxygen; and 100 parts of the respired ail', minus the 3*68 

 parts of carbonic acid gas abstracted by the lime-water 

 = 96*32 parts, must contain 



Oxygen. 



32 : 5-58 : : 96-32 : 1679 parts oxygen, 

 and 16-79 parts of oxygen +3-68 parts of carbonic acid gas 

 = 20-47 parts represent the total quantity of oxygen that 

 appeared to have existed in the atmospheric air previous to 

 its having been respired. 



Now as it is very well known that ordinary atmospheric air 

 contains 2 1 per cent, of oxygen and 79 percent, of nitrogen, and 

 that the formation of any quantity of carbonic acid gas must 

 necessarily require precisely its own volume of oxygen ; also, 

 that air when emanating from the moist surface of the cells 

 of the lungs must contain 1*21 per cent, of aqueous vapour at 



