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The Alttndum Crucible as a Substitute for the 

 Gooch Crucible. 



George L. Clark. 



In order to test the efficiency of the recently introduced unglazed 

 Alundum crucible, when used for the purposes in quantitative analytical 

 chemistry generally assigned to the ordinary Gooch crucible, four different 

 series of analyses were undertaken. These involved the determination of 

 silver by precipitation as silver chloride, copper as cuprous sulpho-cyanate, 

 aluminium as aluminium oxide from ignited aluminium hydroxide, and barium 

 as barium sulphate. Such a selection was made in order to obtain as widely 

 different precipitates as possible, as regards size of particles, ease of filtra- 

 tion and media in which produced, and at the same time be in general usage. 



Both the Alundum and Gooch crucibles permit filtration, drying and 

 weighing without disturbing the precipitate, but the porous nature of the 

 former of course does away with the preparation of an asbestos mat. To 

 discover whether or not such an advantage as well as others claimed for the 

 Alundum crucible by its manufacturers, such as capability of withstanding 

 very high temperatures, is sufficient to warrant its wide adoption for use in 

 accurate quantitative analysis, was therefore the object in view in this study. 



One crucible only was used for the determinations in one series, in order 

 to discover what would be the effect of continuous usage and how thoroughly 

 it might be cleaned in preparation for the next analysis. In each case the 

 empty crucible was heated thoroughly for one hour in the drying oven at the 

 temperature at which the precipitate was later to be dried. The apparatus 

 for the filtration was that used with the Gooch crucible, since any more com- 

 plicated or expensive apparatus would per se be a distinct disadvantage. 

 I. The determination of AgNOs as AgCl. 



In these analyses 50 c. c. portions of a solution, each containing .2432 

 grams of pure AgN0 3 were used. In the first trials a solution of Kahlbaum's 

 chemically pure NaCl was used to precipitate the AgCl from the hot solution 

 of AgN0 3 while rapidly stirred. Stirring was continued for two minutes, 

 the precipitate allowed to settle, filtered through the crucible, washed with 

 water and then dried at 140°. 



