366 



PROCEEDINGS OF THE AMERICAN ACADEMY 



been made with pure material, gave the numbers 122, 122, 122.20, 

 and 121.94. The most probable value is 122.07, and the probable 



tained was not perfectly pure, but left, when evaporated, a slight residue, probably 

 arising from its action upon the glass of the retort. The amount of this residue 

 was ascertained, and allowance made for it in the estimation of the weight of the 

 SbOi. The balance upon which the weighings were made was from Oertling in 

 Berlin, and was used for no other purpose during the work. The weighings were 

 always effected by placing a brass weight of 50 grammes in one pan, while the plati- 

 num crucible to be weighed was placed in the other, and brought into equilibrium 

 with it by the addition of weights. The weights were made by Staudinger of Gies- 

 sen expressly for this purpose ; they were entirely of platinum, from 10 grammes 

 downwards, and so accurately adjusted, that, although the balance indicated the 

 0.00005 of a gramme, not the slightest discrepancy could be observed in comparing 

 different combinations of equal value. 



To prevent loss by eflfervescence in the action of the acid, the platinum crucible 

 was provided with an arrangement consisting of a perforated plate of platinum fit- 

 ting the inside of the crucible, and having attached to it at some little distance a 

 concentric disk of the same metal, and of greater diameter than the perforation in 

 the plate. 



The antimony was reduced to the finest powder in an agate mortar, and acted 

 upon at first with a somewhat diluted acid, in order to prevent a too violent effer- 

 vescence. But as the product then was cliiefly nitrate of oxide of antimony, and 

 it was possible, although not probable, that, if ignited in this state, a portion of the 

 oxide might be volatilized, it was subsequently treated with concentrated acid, to 

 convert it as fully as possible into antimonic acid, and evaporated in an air-bath 

 to dryness. 



To protect the contents of the crucible during the ignition from the reducing ac- 

 tion of the flame, it was inserted in a hole in the centre of a i>late of sheet-iron, a 

 tightly fitting ring of platinum having been interposed between the crucible and the 

 iron.* Of 14 determinations, 4 were rejected as unreliable ; the results of the re- 

 maining 10 are exhibited in the following table. 



The letters a, b, c in the second column denote three different preparations of 

 * Fur a more detailed description of the apparatus I must refer to the original paper. 



