1820.J the Atoms of Bari/tes, Potash, Soda, ^'c. 329 



weights which I have given as my own are those which will be 

 found in the fifth edition of my System of Chemistry, where I 

 have stated the reasons which "indiiced me to pitch upon them 

 The reader will perceive that they are all multiples of 0-125, the 

 weight of an atom of hydrogen. Dr. Prout was the first person 

 who pointed out the important fact that the weights of the atoms 

 of all bodies are multiples of the weight of an atom of hydrogen.* 

 The greater number of the weights which he assigned in his 

 important paper are the same, or nearly the same, with those 

 which I have given as my own. This coincidence was the more 

 gratifying to me, because I had determined upon the numbers 

 above assigned before 1 was aware of his conclusions. But the 

 general law, that the tveights of the atoms of all bodies are multi- 

 ples of the atom of hi/drogeu, belongs exclusively to Dr. Prout. 

 I consider it as the third great step in our investigation of the 

 atomic theory, and I have not a doubt that it will hereafter prove 

 most important and most prolific. I adopted it in the fifth 

 edition of my System of Chemistry, and was enabled by my 

 knowledge of it to come much nearer the true numbers than I 

 otherwise could have done. 



The greater number of chemical writers in this country have 

 adopted the atomic weights assigned by Dr. Wollaston. This 

 was the natural consequence of the introduction of his scale of 

 chemical equivalents, which must be found so useful in every 

 laboratory. The weights assigned in that scale are certainly in 

 general very near the truth ; but as very few of them are abso- 

 lutely correct, they who employ that scale will fall into small 

 errors, of no consequence in many cases, but sufficiently great 

 to be very perceptible, when experiments of the very delicate 

 nature that distinguish those which constitute the subject of the 

 present paper are to be tried. 



Let us now compare the atomic weights as assigned by Dal- 

 ton, Wollaston, and Berzelius, with mine. I reckon the weight 

 of an atom of barytes 9-75. Mr. Dalton's weight, 9-7128, 

 comes nearest this number; but it is less. Dr. Wollaston's, 

 9-7, is still less ; while that of Berzelius, 9-5693, is the least of 

 all. My number is a multiple of the atom of hydrogen, for 

 0-125 X 78 = 9-75; but neither the number of Dalton, Wollas- 

 ton, nor Berzehus, is a multiple of 0-125. My number is easily 

 recalled to memory ; but it would not be an easy task to remem- 

 ber such comphcated numbers as that of Berzelius. 



My number for sulphuric acid agrees exactly with that of Dr. 

 Wollaston, both being 5. That of Berzehus is only a very little 

 greater; namely, 5-0116; while that of Dalton is a very little 

 less, being 4-8571. My number is a multiple of 0-125; for 

 0-125 X 40 = 5; while neither the number of Berzelius nor of 



• Annals of Philusophu, vol. vi. p. S'il. 



