140 atomic weight determinations. 



Thomson Further Determined — 



Antimony at 132 by oxidation. 



Boron at 12 from analysis of borax. 



Mercury at 200 by conversion of the oxide into chloride. 



Tin at 116 by oxidation with nitric acid. 



REDUCTION OF WEIGHINGS TO VACUUM. 



In discussing the analyses recorded in the foregoing pages, 

 or in reconciling atomic weight determinations by various 

 chemists, it may be found convenient to employ the follow- 

 ing table. The maximum error involved is less than 0.01 

 per cent, or 0.1 milligram per gram. 



GRAM weights BEING OF BRASS, FRACTIONS OF PLATINUM. 



For substances the sp* gr. of which exceeds 6.1; no cor- 

 rection is necessary. 



For substances the sp. gr. of which is less than 6.1 : — 



To correct the entire grams ; multiply their number by the 

 correction in the table opposite the sp. gr. of the substance, 

 found in the first column, and add the product to the observed 

 weight. 



To correct the fractions of a gram, multiply the correction 

 opposite the sp. gr. of the substance, found in the third col- 

 umn of the table, by the first two decimal figures of the 

 observed weight, if the sp. gr. of the substance is less than 

 3, and by the first decimal only, if the sp. gr. exceeds 3, and 

 add the product to the observed weight. 



ALL weights used BEING OF PLATINUM. 



For substances the sp. gr. of which exceeds 7.8, no correc- 

 tion is necessary. 



For substances the sp. gr. of which is less than 7.8 : — 

 Multiply the correction opposite the sp. gr. of the substance, 

 found in the third column, by the number of grams, tenths 

 and hundredths observed, if the sp. gr. falls short of 3, or 

 by the number of grams and tenths, if the sp. gr. exceeds 

 3, and add the product to the observed weight. 



The table shows within what limits it is necessary to know 

 the sp. gr. 



