Specific Gravity of Vapours and Gases. 



13 



of weight, without the volume, the pressure, and the tempera- 

 ture of these gases and vapours being known. By means of this 

 method the errors of weighing, arising from the hygroscopic 

 nature of the glass, from the variable amount of aqueous vapour 

 in the balance-case, and from changes of temperature and pres- 

 sure, are satisfactorily eliminated. The degree of exactitude of 

 which the method is capable may be judged from the following 

 experiments, which were performed with a balance weighing up 

 to 100 grammes. I give first of all six carbonic-acid determi- 

 nations, in which both the gas and the dry atmospheric air were 

 freshly filled-in each time, and the temperature of the thermostat 

 varied to between 10° C. and 15° C. 



No. 



Experiment 



Experiment 



Experiment 



Experiment 



Experiment 



Experiment 



I. 



II. 



III. 



IV. 



V. 



VI. 





+0-3200 



+ 0-3200 



+ 0-3200 



' + 0-3300 



+0-3200 



+0-3200 



+0-595 



+0 196 



-0104 



+ 0-066 



-0-508 



-0262 



Tq 



-0010 



-0-516 



-0-400 



+0-950 



+0141 



+0079 



m 



+4-0 



+ 4-0 



+3-4 



+4-2 



+5-4 



+5-0 



m v 



+ 7-0 



+ 6-0 



+9-3 



00 



+ 9-4 



+ 90 



Aiv 



-0-00068 



-0-00068 



-0-00068 



-000068 



-0-00068 



-0-00068 



A i 



-000043 



-000043 



-000043 



-000043 



-000043 



-0 00043 



X 



+0-00085 



+ 0-00085 



+0-00085 



+ 0-00085 



+ 000085 



+000085 



Vy 



+0-2100 



+ 0-2100 



+0-2100 



+ 0-2100 



+02100 



+0-2100 



r v 



+0-516 



+0-409 



-0-508 



+0-354 



+0016 



-0-250 



r h 



+0-975 



+0-253 



-0-025 



-0-466 



-0-387 



+0-050 



m l 



+ 4-0 



+4-0 



+3-2 



+4-4 



+ 6-0 



+54 



m v 



+6-0 



+50 



+ 66 



+ 6-0 



+7-0 



+7-0 



A„, 



-0-0003 



-00003 



-0-0003 



-0-0003 



-00003 



-00003 



A, 



-0 00051 



-000051 



-000051 



-0-00051 



-0 00051 



-000051 



d 



+ 0-00074 



+0-00074 



+0-00074 



+0-00074 



+0-00074 



+0-00074 



From these data for calculation, the following values are got 

 for the specific gravity of carbonic acid : — 



1 1-525 



II 1-525 



III 1-528 



IV 1-529 



V 1-528 



VI 1-529 



In none of the experiments did the weight of carbonic acid 

 exceed # 35 grm. According to Regnault's classical researches 

 carried out with more than 19 grms. of carbonic acid, the specific 

 gravity of this gas was 



1-52901. 



The same vessels were employed for the determination of the 



