Notice of some recent additions to Chemistry. 69 



air is not even yet satisfactorily determined, in the opinion of all 

 chemists. According to Dumas, the atmosphere consists of (Ann. 

 de Chim. iii. 267.) 



By Weight. 

 Oxygen, . . . . . 23. 

 Azote, 77. 



And dividing these numbers by what he has found to be the specific 

 gravities of the gases, he deduces the composition in bulk to be 

 23 77 



YYq^j = 20-80 Oxygen, + 972 = ^^'^^ ^^^*®' 



Calculation, however, shows that the specific gravity of oxygen, 

 according to his data, ought to be M066 or M067; and we believe 

 Dumas considers that the true specific gravity cannot be under 1-107. 

 Dumas has lately published some experiments made at Copenhagen, 

 on air taken from the surface of the ocean, where the ratios of the 

 gases vary considerably from these data, as follows : — 



By Bulk. By Bulk. 



By Weight. Sp. Gr. Mill. Sp. Gr. M067. 



Oxygen, .... 22-58 20-3 2040 



Azote, .... 77-42 79-7 79-60 



It deserves remark, that the mean of six experiments out of ten, made 

 by Dr. Thos. Thomson, (First Principles, I. 98.) gave for the composi- 

 tion of air at Glasgow, by bulk — 



Oxygen, . . . 20*42 Azote, . . . 79-58 



This remarkable coincidence between the composition of the air at 

 the sea, where vegetation is absent, and of that in the oxygen consum- 

 ing city, perhaps deserves more attention than has yet been paid to it 

 In connection with experiments upon pure air, the trials of Leblanc 

 upon vitiated atmospheres are of high interest. The quantity of car- 

 bonic acid in the atmosphere in the normal state has been shown by 

 the Saussures to vary from 3 to 6 parts in 10000. Leblanc (Ann. de 

 Chim. V. 223.) has examined the quantity in crowded rooms, theatres, 

 cities, &c. In the hospital La Pitie, the air of one of the wards con- 

 taining 54 patients, afiforded y^^^ of COjj, or 5 times more than that 

 of normal air. Under similar circumstances, at the Salpetriere, the 

 quantity was y^%^. In Dumas' class-room, after a lecture of an hour 

 and a half, where 900 persons were present, the carbonic acid amounted 

 to 1 per cent, and the same quantity of oxygen had disappeared. 

 From other experiments, he considers this a maximum quantity for 

 safety, and strongly recommends a better ventilation when so much 

 carbonic acid is present. This result agrees with experiments made 

 in this country. When the atmosphere is deteriorated by burning 

 charcoal, he has seen deatli produced when 3 per cent, of carbonic 

 acid was present in the atmosphere. In all such cases of death from 

 stoves, he has found carbonic oxide in the air, and he attributes a 



