150 Intelligence and Miscellaneous Articles. 



oxygen blowpipe, of which the efficacy requires the simultaneous 

 presence of oxygen and the most intense heat. It might be fused 

 by exposure in vacuo to the discharge of a powerful voltaic series, 

 by means of the apparatus of which a description with engravings 

 has been given in a recent volume of the Transactions of the Ame- 

 rican Philosophical Society, and republished in ' Silliman's Journal' 

 for 1841, vol. xl. p. 303. 



I have obtained osmium by heating the osmiate of ammonia in a 

 glass tube with sal-ammoniac, agreeably to the instructions given by 

 Berzelius. In this way a result was obtained which the information 

 given by that distinguished chemist had not led me to anticipate. 

 The tube became coated with a ring of osmium, which it would be 

 impossible by inspection merely to distinguish from the arsenical 

 ring on the peculiar features of which reliance has been placed for 

 the detection of arsenic. 



It follows from my experiments and observations, that of all 

 metallic bodies, osmiuret of iridium is the most difficult to fuse ; 

 that rhodium and iridium are both fusible by the hydro-oxygen blow- 

 pipe, properly employed ; that the former has the rosy whiteness of 

 bismuth, the latter the pale white of antimony ; and that both of 

 them are slightly sectile, though extremely hard and nearly un- 

 malleable ; that iridium merely fused is heavier than platinum con- 

 densed by the hammer. Thus it follows from my experiments, and 

 from the recent observations of Breithaupt, on some specimens of 

 native iridium, that the metal, whether in this state or pure as ob- 

 tained by chemical skill and consolidated by fusion, must be allowed 

 that pre-eminence in density, which, until of late, was given to 

 platinum. 



It may be proper to add, that subsequently to the writing of the 

 preceding narrative, receiving some large quantities of iridium and 

 rhodium from Messrs. Johnson and Cock, my experiments were 

 successfully repeated on a larger scale, but without any result be- 

 sides that of confirming the facts above stated. — Silliman's Journal 

 for Nov. 1846, p. 365. 



NOTE ON THE MEANS OF TESTING THE COMPARATIVE VALUE 

 OF ASTRINGENT SUBSTANCES FOR THE PURPOSES OF TAN- 

 NING. BY ROBERT WARINGTON, ESQ. 



Having been frequently called upon to examine the value of 

 astringent substances imported into this country for the purposes of 

 tanning, such as valonia, divi-divi, sumac, cutch, &c.,-I am induced 

 to believe that the detail of the manipulation adopted may not be 

 without interest to some of the members of the Society. As the 

 manufacture of leather was the object of the purchaser of these 

 materials, gelatin was selected as the basis for the estimation of 

 their comparative value ; and after several trials with various kinds of 

 natural and manufactured gelatin, such as varieties of isinglass, glue, 

 patent gelatin, &c., the finest long staple isinglass was found to be 

 the most constant in its quality and least liable to undergo change. 



