106 THE ATOMIC WEIGHTS. 



The second series of determinations was essentially like the first, ex- 

 cept that auric bromide was taken instead of the chloride. The ratio 

 measured, Ag^ : Au, is precisely the same as before. Results as follows : 



Ratio. 

 60.929 

 60.91 1 

 60.945 

 60.916 

 60.919 

 60.941 



Mean, 60 927, ± .0038 



Hence Ag : Au : : 100 : 182.781, ± .0114. 



In the third series of experiments the salt KAuBr^was taken, purified 

 by five recrystallizations. The solution of this was weighed out into 

 nearly equal parts, the gold being measured as in the two preceding 

 series in one portion, and the bromine thrown down by a standard silver 

 solution as before. This gives the ratio Ag, : Au : : 100 : x. 

 Au. Ag. Ratio. 



5-7048 12.4851 45-693 



7-9612 17.4193 45 



2-4455 5-3513 45 



4-1632 9- 1 153 45 



693 

 699 

 673 



Mean, 45.689, =b .0040 



Hence Ag : Au : : 100 : 182.756, ± .0160. 



The fifth series of determinations, which for present purposes naturally 

 precedes the fourth, was electrolytic in character, gold and silver being 

 simultaneously precij^itated by the same current. The gold was in solu- 

 tion as potassium auro-cyanide, and the silver in the form of potassium 

 silver cyanide. The equivalent weights of the two metals, thrown down 

 in the same time, were as follows, giving directly the ratio Ag : Au : : 100 : x. 



Au. Ag. Ratio. 



5.2721 2.8849 182.748 



6.3088 3-4487 182.933 



4-2770 2.3393 1S2.832 



3.5123 1-9223 1S2.713 



3.6804 2.0132 1S2.S14 



Mean, 1S2.808, ± .0256 



This mean may be combined with the preceding means, and also with 

 the determination of the same ratio by Thorpe and Laurie, thus : 



Thorpe and Laurie 182.S27, zh .0101 



Mallet, chloride series 182.730, dz .0102 



Mallet, bromide series. , 182.781, zb .01 14 



Mallet, KAuBr^ series 182 756, ± .0160 



Mallet, electrolytic 182.808, rb .0256 



General mean 182.778, dr -0055 



