26 



Prof. Sir C. A. Cameron and Mr. J. Macallan. [May 2, 



Table II. 



Percentage of anhydrous 





selenic acid. 



Specific gravity. 



99-73 



2-6083 



99-50 



2-6051 



99-00 



2-5975 



98*50 



2-5863 



98-00 



2-5767 



97 50 



2-5695 



97-00 



2-5601 



96-00 



2-5388 



95-00 



2-5163 



94-00 



2-4925 



93-00 



2-4596 



92-00 



2-4322 



91-00 



2-4081 



90-00 



2-3848 



89-00 



2-3568 



88-00 



2-3291 



87-00 



2-3061 



86-00 



2-2795 



85-00 



2-2558 



84-00 



2-2258 



83-00 



2-1946 



82-00 



2-1757 



81-00 



2-1479 



80-00 



2-1216 



79-00 



2-0922 



73-50 



1-9675 



The rate of increase of specific gravity is not uniform for equal 

 increments of strength. It diminishes as the strength, increases, as in 

 the case of sulphuric acid, but not regularly. The diminution is very- 

 marked at the highest strengths. When sulphuric acid has arrived 

 at the greatest strength attainable by ebullition — 98'66 per cent. — its 

 specific gravity is stated to decrease until the anhydrous acid, 

 H 2 S0 4 , is reached. Selenic acid behaves dissimilarly in this respect ; 

 the increase of its specific gravity, although not uniform, is main- 

 tained throughout. 



Berzelius (' Traite de Chimie,' 1830) mentions that selenic acid of 

 95'9 per cent, strength has a specific gravity of 2'6. Fabian gives 

 2-609 as the specific gravity of an acid of 94*9 per cent, strength, and 

 2-627 for an acid of 97'4 per cent. It will be seen that these results 

 do not agree, nor are they consistent with those we have obtained. 

 If values for the strengths mentioned be calculated from the foregoing 



