SILVER, POTASSIUM, ETC. 53 



all there are nineteen ratios, involving about two hundred and fifty 

 separate experiments. These ratios may now be tabulated and num- 

 bered for reference, it being understood that the probable error in each 

 case is that of the last term in the proportion. 



(i.) Percentage of O in KCIO3 39-154, ± .00038 



(2.) " " KB1O3 28.6755, ± .0207 



(3-) " " KIO3 22.473, ±.0050 



(4.) " ' NaC103 45.0705, dr .0029 



(5.) " " AgC103 25.080, d= .0010 



(6.) " " AgBr03 20.349, zfc .0014 



(7-) " " AglOg 16.9771, ± .0009 



(8.) Ag : NaCl : : 100 : 54.2071, ± .00018 



(9.) Ag : NaBr : : 100 : 95.4405, zfc .0007 



(10.) Ag : KCl : : loO : 69.1143, d= .00013 



(11.) Ag : KHr : : 100 : 110.3459, zfc .0019 



(12.) Ag : KI : : lOO : 153.6994, zh .0178 



(13.) Ag : CI : : 100 : 32.8418, zfc .0006 



{14.) Ag : Br : : 100 : 74.080, zfc .00057 



(15.) Ag : I : : 100 : 117.5345- ± -OOOQ 



(16.) AgCl : NaCl : : loo : 40.867, zfc .0033 



(17.) KCl : AgCl : : 100 : 192.294, zfc .0029 



(18.) AgCl : AgBr : : 100 : 131.030, zfc .023 



(19.) AgCl : Agl : : 100 : 163.733, zfc .0076 



Now, from ratios 1 to 7, inclusive, we can at once, by appl^ying the 

 known atomic weight of oxygen, deduce the molecular weights of seven 

 haloid salts. Let us consider the first calculation somewhat in detail. 



Potassium chlorate yields 39.154 per cent, of oxygen and 60.846 per 

 cent, of residual chloride. For each of these quantities the probable 

 error is ± .00038. The atomic weight of oxygen is 15.879, ± .0003, so 

 that the value for three atoms becomes 47.637, ± .0009. We have now 

 the follow^ing simple proportion : 



39.154 : 60.846 : : 47-637 = ^', 



whence the molecular weight of potassium chloride becomes = 74.029. 

 The probable error being known for the first, second, and third term 

 of this proportion, we can easih^ find that of the fourth term by the 

 formula given in our introduction. It is ± .0073. By this method we 

 obtain the followdng series of values, which may conveniently be num- 

 bered consecutively with the foregoing ratios : 



(20) KCl, from (i) ^ 74.029, zt .0073 



(21) KBr, " (2) = 118.487, zfc .0923 



(22) KI, " (3) == 164.337, ± .0382 



(23) NaCl, " (4)= 58.057, ± .0050 



(24) AgCl, " (5) = 142.303, zfc .0066 



(25) AgRr, " (6) = 186.463, zfc .0137 



(26) Agl, " (7)3^232.959, fcz. 0134 



