64 ATOMIC WEIGHTS OF SODIUM AND CHLORINE. 



nitric and hydrochloric acids was then evaporated to dryness upon a 

 clean steam bath under an appropriate hooded cover (Victor Meyer 

 funnel). The atmosphere around was kept as pure as possible during 

 this evaporation, which was usually conducted during the night. 

 Finally the silver chloride was fused in the quartz dish supported inside 

 of a large porcelain crucible from which the products of combustion 

 of the gas-flame were suitably deflected. The weighed cover caught 

 the one or two minute drops projected upward during the act of 

 fusion. Then a mixture of chlorine and hydrochloric acid gas was 

 passed in, so as to convert any residual traces of nitrate of silver 

 wholly into argentic chloride. The precaution of cooling, mentioned 

 on p. 59, enabled us to preserve the quartz dish intact through the 

 analyses, notwithstanding the extreme fragility of thin fused quartz. 

 Its weight was conserved through three experiments within the limits 

 of the accuracy of the weighing. Experiments 83, 84, and 85 were 

 made by this method. One of these is given below in detail as an 

 example of the method. 



Experiment 84. 



Grams. 



Corrected weight of silver in air 6.25336 



Vacuum correction 0.00018 



Weight of silver in vacuum 6.25318 



Excess weight quartz dish over counterpoise 0.215 10 



Excess weight dish and fused AgCl over counterpoise 8.52279 



Weight of argentic 'chloride in air 8.30769 



Excess weight cover glass over counterpoise 0.09972 



Excess weight cover and spattering over counterpoise 0.09974 



Spattering 0.00002 



Weight argentic chloride in air 8.30771 



Vacuum correction 0.00061 



Weight of argentic chloride in vacuum 8.30832 



AgCl found in desiccator by nephelometer 0.00002 



Total weight of argentic chloride 8.30834 



AgCl = 6.25318 : 8.30834 = 100.000 : 132.866 



This second method, which avoids any transference of material 

 whatever, is an unusually searching check upon the method employing 

 the Gooch filter ; and that the two methods confirm each other to the 

 limit of weighing is a most satisfactory criterion of each, supporting 

 the previous similar work with sodic chloride as well. 



