APPENDIX. 



DETERMINATIONS BY T. THOMSON. 



In Thomson's Annals of Philosophy, volumes 16 and 17, 

 1820-21, Thomson published a series of papers descrip- 

 tive of experiments undertaken for the purpose of verifying 

 Front's hypothesis. His method consisted in mixing re- 

 agents in what he considered equivalent proportions, and 

 after precipitation examining portions of the supernatant 

 liquid for an excess of each of the salts supposed to neu- 

 tralize one another. In all except four cases, either the 

 salt analyzed was a sulphate and the precipitant barium 

 chloride, or the determination was dependent upon such 

 an analysis ; yet although Thomson took barium = 70, in 

 no instance was he able to detect either barium or sul- 

 phuric acid in the residual solution when the quantity of 

 the re -agents corresponded to the atomic weights which he 

 adopts. Comparison of his results with those reached by 

 more accurate experimenters will make this exact neutrali- 

 zation appear impossible, nor were his contemporaries able 

 to repeat his experiments successfully. Thomson's deter- 

 minations are, as such, utterly valueless, yet as they were 

 for many years extensively accepted in English and Ameri- 

 can scientific literature they are inserted here for reference. 

 In the following table Thomson's numbers are multiplied, 

 when necessary, for the sake of comparison with the values 

 now accepted. 



Determinations Involving Barium = 70. 



Arsenic 76 Magnesium 24 



Barium 140 Manganese 56 



Bismuth 216 Nickel 52 



Calcium 40 Nitrogen 14 



Carbon 12 Phosphorus 32 



Chlorine 36 Potassium 40 



Chromium 56 Silver 110 



Cobalt 52 Sodium 24 



Copper 64 Strontium .. 88 



Iron 56 Sulphur 32 



Lead 208 Zinc 68 



139 



