ON THE ATOMIC WEIGHT OF CHLOEINE. 



187 



the same volume as the bulb in the subsequent experiments, since the maximum 

 variation in the displacement of the bulb did not exceed 1'3 cub. centim. This 

 variation in volume, caused by differences in sealing off the thick-walled capillary 

 tube, may be assumed to be due to the solid glass drop at the sealed end. When the 

 density of the air altered between the first and second weighings of the bulb, a 

 difference between the displacement of the bulb and the counterpoise might affect the 

 apparent weight of the bulb, but in only one experiment (No. 8) was a correction 

 necessary, and that only a unit in the fifth place of decimals. 



The weighings of the chlorine bulb were carried out in the same manner, with a 

 similar glass counterpoise. It was not, of course, necessary to obtain the same degree 

 of accuracy in weighing the chlorine as in weighing the hydrogen, since a unit in the 

 fourth place of decimals is insignificant. Variations in the displacement of the 

 chlorine bulb, caused by sealing-off, though considerably larger than those of the 

 hydrogen bulb, did not affect the determination of the " chlorine taken." 



In illustration of the method of weighing we may refer to Experiment V. The 

 palladium bulb (charged with hydrogen) required the following weights to be added 

 to the opposite pan : 



Weights used. 



Value. 



Brass 20 grammes 



Ft '5 



02 



01 (1) 



01 (2) 



Pt rider on 2nd division 



19-99973 grammes 

 49998 

 02001 

 01001 

 01000 

 00201 



20-54174 grammes 



Five weighings with the weights in the right-hand pan gave a mean zero of 

 398 '2 divisions on the sale. Four weighings with the weights reversed gave a mean 

 zero of 597. With no load the mean zero was 497. The two differences are : 



Eight 98-8. Left lOO'O. Mean 99'4. 



The sensibility under this load was found to be 202 divisions of the scale for a 

 difference of 1 milligramme. The mean displacement of the zero was, therefore, equal 

 to a weight '00049 gramme to be subtracted. 



Adding these weights together 



Counterpoise + 400 00097 grammes 

 Weights + rider + 20-54174 

 00049 



420-54222 



2 B 2 



