408 ' Scientific Intelligence. 



It is not, however, necessary to suppose that all the oxyds crystalliz- 

 ing in the regular system, have the same atomic volume. ' We know 

 by the study of polymeric bodies, that the same elements may be differ- 

 ently condensed : thus a volume of elaldehyde in vapor contains three 

 times as much carbon, hydrogen and oxygen, as the same volume of 

 aldehyde in the same state. A similar relation may exist for solids and 

 liquids. A volume of an oxyd may contain 0M 2 , 2 M 4 or 3 M 6 , or 

 in general OnM 2 n, but if the atomic volume of an oxyd 0M 2 is V, the 

 volume of its polymere will be V n . There may then be oxyds crystal- 

 lizing in regular octahedrons, having an atomic volume different from 

 that of the preceding oxyds. 



The protoxyd of copper Cu 4 0, and the arsenious anhydride As 2 3 , 

 are illustrations in point ; if we calculate the atomic volume of these 

 oxyds, reducing their formulas to the expression OM 2 , we obtain 23*6 

 for one and 18*0 for the other ; these numbers are approximate multi- 

 ples of the atomic volume of the preceding minerals by 2 and 1£. It 

 is as if the molecule of protoxyd of copper* was 2 Cu« 4 - and that of 

 arsenious anhydride Ol£As<* 3 in relation to the molecule 0M 2 of those 

 minerals. Beside this we do not indicate whether the type in which 

 we have placed these last, be OM 2 more than 2 M 4 , (OM 2 ,OM 2 ) or 

 3 M 6 =(OM 2 , OM 2 , OM 2 ) ; we shall be able to establish our consider- 

 ations upon all other formulas, provided that it is the same for all the 

 oxyds. It is nothing in effect but a question of ratios. 



2. On the Acid contained in the North American Columbite; by 

 Henry Rose, (L., E. and D. Phil. Mag., xxx, 360, from Poggend. An- 

 nal.) — The columbite of North America has the same crystalline form 

 as that from Bodenmais and Bavaria, but is distinguished from it in 

 general by a lower specific gravity ; however, we find the same differ- 

 ence in the specific gravity of the American mineral as occurs in the 

 different crystals of the Bodenmais columbite. The lightest crystals 

 from the last locality have the same specific gravity (5*704) as the 

 heaviest crystals from North America (5.708). 



I have already communicated two analyses of North American co- 

 lumbites, one of which however it was doubtful whether it came from 

 America. The following analysis of American columbite was made by 

 M. Grewink in my laboratory : it yielded, 



Acid, . . . - . 80-06 



Protoxyd of iron, . . . 1259 



Protoxyd of manganese, . . . 5*97 



Oxyd of tin, .... 0-96 



Oxyd of copper and lead, . . . 0-44 



io^oi 



The specific gravity in fragments was 5*323 ; in powder, 5-3202. 



This columbite comes nearest in composition and also in speci 

 gravity to that examined by M. Schlieper. . - {y 



I have on a former occasion shown that the different specific ? raVl ^ 

 of the crystals of the Bavarian columbite was owing to the ^ ev ^ n } ^ flt 

 portions of niobic and pelopic acids which are found in the dinef^ 



* Cua=Cu 2 , cuprosum; As a =AsJ arseniosum 



