342 PROCEEDINGS OF THE AMERICAN ACADEMY 



XXII. 



ON A NEW METHOD FOR THE SEPARATION AND SUBSE- 

 QUENT TREATMENT OF PRECIPITATES IN CHEMICAL 

 ANALYSIS. 



By F. a. Gooch. 



Presented Feb. 13, 1878. 



The introduction of Bunsen's method of filtration and immediate igni- 

 tion of precipitates in the moist condition has left little to be desired 

 as regards accuracy of result and rapidity of execution, in the treat- 

 ment of precipitates which may be submitted to high temperatures in 

 contact with carbonaceous matter. In analytical methods which require 

 that filter-paper and precipitate shall be ignited apart, or dried together 

 at a temperature below the point at which paper begins to char, the 

 same degree of exactness has not, in general, been hitherto attained. 



To obviate the difficulty of bringing a paper-filter of ordinary dimen- 

 sions, particularly when covered with a voluminous precipitate, to a 

 definite condition of desiccation, the sand-filters of Dr. Gibbs and 

 Taylor,* the porous cones of Munroe.f and finally the process of 

 reverse filtering, first applied to quantitative work by Carmichael,t 

 improved by Casamajor,§ and thoroughly elaborated by Professor 

 Cooke.ll have been successively brought forward. 



The latter process gives most excellent results in the separation of 

 precipitates which settle quickly and completely ; and, inasmuch as 

 many precipitates which of themselves are not inclined to fall rapidly 

 may be made to do so by proper treatment (by boiling, for example, 

 the addition of ammonium salts, Chatard's^ method of granulating gela- 

 tinous precipitates, or other similar device), the field of usefulness of 

 this process is wide. 



The sand- filters in skilful hands, and the porous cones with no more 

 than ordinary care, give accurate results, and possess moreover the 



* Am. Jour. [2], vol. xliv. p. 215. t Am. Jour. [3], vol. i. p. 1. 



J Zeitschr. f. Chem. [n.f.], Bd. 6, p. 481. § Am. Cliem. vol. v. p. 441. 



II These Proceedings, vol. xii. p. 124. H Am. Jour. [2], vol. 1. p. 247. 



