50 On the Daltonian Theory of [July. 



Wfight of an atom. 



60. Tellurium 4-107 " 



61. Arsenic 6-000 ' 



62. Cobalt 7-326 m 



63. Manganese 7'130 n 



64. Uranium 12-000 ° 



65. Molybdenum 5'882 * 



k According to Berzdius the only oxide of tellurium known 

 is a compound of 100 metal -f 24-83 oxygen. Hence the 

 number in the table. 



1 We know two combinations of arsenic and oxvgen ; the first 

 contains 100 metal + 33*333 oxygen, the second 100 metal + 

 50 oxygen. These are to each other as 2 to 3 ; hence the first 

 must contain 2 atoms of oxygen, the second 3. Hence the 

 number in the table. Berzelius speaks of an oxide of arsenic 

 composed of 100 metal + 8-333 oxygen. If it exist, an atom 

 of arsenic will weigh 12-000. {Ann. de Ch'nn. lxxxiii. 118.) 



m We know two oxides of cobalt, the blue and the black. 

 These, from the analysis of Rolhoff, are composed of 100 metal 

 united with 27'3 and 40-95 of oxygen. (Berzelius, L'drhok i 

 Kemien, ii. 29/.) These numbers are to each other as 2 to 3. 

 Hence the first must be a deutoxide. 



n Berzelius describes five oxides of manganese : but his first, 

 from the way in which he obtained it, is exceedingly doubtful. 

 I reject it therefore. The first of the other four is green, the 

 second olive, the third brown, and the fourth black. Their 

 composition he states as follows : — 



1 of 100 metal + 14-0533 



2 100 + 2S-107 



3 100 + 42-16 



4 100 + 56-213 



These numbers are to each other as the numbers 1, 2, 3, 4. 

 Hence the first is a protoxide, and gives the weight of an atom 

 of manganese as in the table. If Berzelius' first oxide really 

 exist, we must double the weigiit of an atom of manganese. 



° From Bucholz' experiments there seem to be two oxides of 

 uranium, the black and the yellow; the first composed of about 

 100 metal + 8-333 oxygen, the second of 100 metal + 25 

 oxygen. These two numbers are to each other as 1 to 3. Hence 

 the number in the table. 



r We know two oxides of molybdenum, the blue and the 

 white, composed, according to Bucholz, of 100 metal and 34 

 and 50 oxygen. Now these numbers are. to each other as 2 to 3. 



