THE ELEMENTS OF THE CHEMIST 131 



which the chemist had not hitherto taken cognisance. And so it 

 turned out. With most remarkable confidence in the trust- 

 worthiness of his scheme as indicating a law of nature, MendeleefE 

 proceeded to describe in detail the properties, chemical and 

 physical, which would be exhibited by substances corresponding 

 to the vacant places in the table, and in truly prophetic spirit to 

 predict their discovery. 



In 1871 the atomic weights represented approximately by the 

 numbers 44, 70, and 72 were not known to belong to any existent 

 element, but to the hypothetical elements expected to fill these 

 places Mendeleeff: gave the names ekaboron, ekaluminium, and 

 ekasilicon. In a footnote contained in his famous work on 

 The Principles of Chemistry, the English translation of 1891 

 contains the following words : 



" When in 1871 I wrote a paper on the application of the 

 periodic law to the determination of the properties of yet un- 

 discovered elements, I did not think I should live to see the 

 verification of this consequence of the law, but such was to be 

 the case. Three elements were described ekaboron, ekalu- 

 minium, and ekasilicon 1 and now, after the lapse of twenty 

 years, I have had the great pleasure of seeing them discovered 

 and named after those three countries where the rare minerals 

 containing them are found, and where they were discovered 

 Gallia, Scandinavia, and Germany." 



Between the elements zinc and arsenic then there were two 

 unoccupied places, and the following are the chief properties 

 which, according to the law, should appertain to them. 



The following is the account given by Mendeleeff of the first 

 of these : 



" Zinc, which has an atomic weight 65, should be followed in 

 the III group by an element with an atomic weight about 69. 

 It will be in the same group as aluminium, and should conse- 

 quently give R 2 0s5 RC1 3 , R 2 (S0 4 ) 3 , alums and like compounds 

 analogous to those of aluminium. Its oxide should be more 

 easily reducible to metal than alumina, just as zinc oxide is 

 more easily reducible than magnesia. The oxide R 2 3 should, 

 like alumina, have feeble but clearly expressed basic properties. 

 The metal reduced from its compounds should have a greater 

 atomic volume than zinc, because in the fifth series, proceeding 

 from zinc to bromine the volume increases. And as the volume 



1 Eka = Sanscrit meaning one, 



