98 schaller: calculation of mineral formulas 



The ratios are sufficiently close to 11 : 2 : 8 to show that these 

 are the correct numbers. In reality the ratios are very much 

 closer to 11 : 2 : 8 than the figures given by Van Horn and Cook 

 suggest, as will be shown below. 



The first column from the ratios given above is reproduced 

 below (1) with the molecular proportions for silver and copper 

 combined, and all the quantities multiplied by 100 for conveni- 

 ence of calculation. When the lowest number is taken as unity 

 it is readily seen that the ratios are approximatly 5^ : 1 : 4. 

 If the first figure be divided by 2 times 5| (these numbers are 

 doubled to avoid fractions), the second by 2 X 1, and the third 

 by 2 X 4, the figures under (2) are obtained. These numbers 

 should be nearly the same. Their average is 4.986. If now the 

 ratios obtained from the analysis be divided by this average value, 

 namely 4.986, the figures given under (3) are obtained which are 

 considerably closer to 11, 2, and 8 respectively, than the ones 

 given by Van Horn and Cook. 



(1) (2) (3) 



S 54.44 4- (2 X 5i) = 4.949 10.92 



As 10,08^(2X1) = 5.040 2.02 



Ag2,Cu2 39.75^(2X4) = 4.969 7.97 



Av. = 4.986 



Ratios such as those given above under (3) are still too far 

 from the whole numbers they approximate for comparison as 

 they stand. The figures should be reduced to multiples of approx- 

 imate unity which can then be directly compared, as follows : 



S 10.92 = 11X0.99(3) =11X0.99 



As 2.02 = 2X1.01 =2X1.01 



Ag2,Cu2 7.97 = 8X0.99(6) = 8X1.00 



These figures show that the ratios deducible from the pearceite 

 analysis are in fact far closer to the whole numbers 11 : 2 : 8 than 

 the ratios 10.80 : 2.00 : 7.886 given by Van Horn and Cook, 

 which were obtained by arbitrarily selecting one of the numbers 

 as unity. The form in* which the last set of ratios is given above 

 appears to express most accurately the relations derivable from 

 the analysis. 



