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ANNUAL OF SCIENTIFIC DISCOVERY. 



proportion as their equivalent numbers diminish, their properties become 

 more and more electro-negative; a corresponding change is also visible in 

 the organic radicals which these elements are capable of forming by their 

 union with carbon and hydrogen. The passage from the positive to the 

 negative sign in the interval between phosphorus and nitrogen, is accom- 

 panied by a marked change in the nature of the organic radicals into which 

 these elements enter; 3(C4 H^) X does not possess the power of combining 

 directly with oxygen, chlorine and sulphur which 3(C4Ho)P, 3(C4 Ho)As, 3 

 (C4Ho)Sb exhibit in so high a degree. The methyl compounds show the 

 same differences as the ethyl. 



Again, if we begin with phosphorus, and form an ascending series with 

 a common difference of 44 (except in one instance), we shall find both the 

 number 164, the double of which constituted the eleventh term of the pre- 

 ceding table, and also the equivalent of bismuth, the double of which 

 formed the thirteenth term of the same table. 



These four elements exhibit strong analogies and are all isomorphous 

 with each other. 



If, takinsr mercury as a starting-point, we subtract the number 44 from 

 each term to find the following one, we shall obtain the series 



