SILVER, POTASSIUM, ETC. 43 



A series was also begun in which one sample of potassium chloride 

 was to be balanced against silver from various sources, but only one 

 result is given, namely, 69.1240. This, with the previous series, gives a 

 mean of 69.1230, .0002. 



Five series of determinations are now at hand for the ratio Ag : KC1. 

 They combine as follows : 



Marignac 69.062, .0017 



Stas, ist series 69. 1036, .0003 



" 2d " 69.1033, .0003 



" 3d " ...., 69. 1190, rb .0003 



" 4th " 69.1230, .0002 



General mean 69.1143, d= .00013 



The difference between the highest and the lowest of Stas' series cor- 

 responds to a difference of 0.021 in the atomic weight of potassium. The 

 rejection of the earlier work might be quite justifiable, but would exert 

 a very slight influence upon our final result. 



The quantity of silver chloride which can be formed from a known 

 weight of potassium chloride has also been determined by Berzelius, 

 Marignac and Maumene. Berzelius * found that 100 parts of KC1 were 

 equivalent to 194.2 of AgCl ; a value which, corrected for weighings in 

 air, becomes 192.32. This experiment will not be included in our dis- 

 cussion. 



In 1842 Marignac f published two determinations, with these results 

 from 100 KC1 : 



192.33 

 192-34 



Mean, corrected for weighing in air, 192.26, .003 



In 1846 Marignac I published another set of results, as follows. The 



weighings were reduced to vacuum, The usual ratio is in the third 

 column : 



17.034 grm. KC1 gave 32.761 AgCl. 192.327 



I4-427 27.749 " 192.341 



15.028 " 28.910 " 192.374 



15.131 29.102 " 192.334 



15.216 " 29.271 " 192.370 



Mean, 192.349, .006 



Three estimations of the same ratio were also made by Maumene as 

 follows : 



*Poggend. Annal., 8, i. 1826. 



f Ann. Chem. Pharm., 44, 21, 1842. 



t Berzelius' I^ehrbuch, sth E}d., Vol. 3, pp. 1192, 1193. 



Ann. d. Chim. et d. Phys. (3), 18, 41. 1846. 



