1818.] the Atoms of Chemical Bodies. 341 



Weight of an atom. 



8 Phosphorus 1-500 d 



9 Azote 1-750* 



10 Sulphur 2-000 



11 Tellurium 4-000 e 



12 Arsenic 4-750 f 



conceive the weight of an atom of silica to be 2*000. But as it 

 must contain at least one atom of oxygen, it is obvious that an 

 atom of silica must weigh 1 . 



d There can be no doubt that this is the true weight of ail 



atom of phosphorus. Perphosphuretted hydrogen gas has the 



specific gravity of 0-9022. The bulk of hydrogen gas is not 



altered by converting it into perphosphuretted hydrogen. Hence 



t is composed by weight of 



Hydrogen 694 or 1 



Phosphorus 8328 . . 12 



1 conceive this gas to be a compound of one atom hydrogen 

 and one atom phosphorus ; but 1 : 12 :: 0*125 : 1*5. Perphos- 

 phuretted hydrogen gas unites with 1 volume, 14- volume, and 



2 volumes of oxygen gas. Now half a volume of the oxygen 

 gas unites to the hydrogen ; the remainder combines with the 

 phosphorus ; so that one volume of phosphorus unites with half 

 a volume, with 1 volume, and with li volume of oxygen, forming 

 hypophosphorous acid, phosphorous acid, and phosphoric acid. 

 This is the same thing as if we said that one atom of phosphorus 

 unites with one atom, two atoms, and three atoms of oxygen 

 respectively. 



e I think it probable that oxide of tellurium is a compound of 

 100 tellurium + 25 oxygen. Berzelius found 100 tellurium 

 + 24*8 oxygen, which comes sufficiently near. Now if this 

 oxide be a compound of one atom metal + one atom oxygen, it 

 is obvious that an atom of tellurium will weigh 4. 



f Experiments on arsenic seem to be attended with more 



• This is the number which Dr. Wollaston selected after a careful exami- 

 nation of the experiments hitherto made on the subject. Mr. Phillips has, with 

 his usual acuteness, shown it to tally very nearly indeed with the best experiments 

 of Davy, Gay-Lussac, Dalton, and his own. — (Royal Institution Journal, v. 162.) 

 I am disposed to consider it as correct. The only experiment which induces me 

 to hesitate is one by Berthollet. He decomposed nitre by heat, and obtained a 

 gas composed of one volume azote and two volumes oxygen : our number would 

 require one volume azote and 2j volumes oxygen. I shall give, a translation of this 

 paper of Berthollet in the next article of the present number, because I wish to 

 draw the attention of chemists to it. 1 do not know very well how to account for 

 this discordance between the results of Berthollet and those of other chemists. Per- 

 haps the half volume of oxygen wanting may have combined with the potash. I 

 may, hereafter, relate the result of a set of experiments which I mean to undertake 

 on purpose to elucidate this point. Till then I think it safest toabide by the num- 

 ber 1*75 for the weight of an atom of azote. 



