SCHEME FOR THE QUALITATIVE DETERMINATION OF SUB- 

 STANCES BY THE BLOW-PIPE. 



By T. Egleston, E. M. 



In tlie course of my instruction in blow-pipe analysis, I formerly 

 found great difficulty in teaching the students how to distinguish with 

 certainty, and within a limited time, the substances contained in a mix- 

 ture of four or five ingredients. The old routine method of examination 

 in the closed and open tube, and then on charcoal, &c., answered very 

 well when not more than one or two substances were present, but did 

 not answer in the hands of beginners when they came to examine alloys. 

 For a long time I was convinced that it was useless to expect of a stu- 

 dent that he should be able, without extended practice, to determine, 

 qualitatively, the composition of a very complex substance. It finally 

 suggested itself to me, however, that a plan similar in some respects to 

 the one used in certain quantitative assays would answer for the gen- 

 eral outline of qualitative work. I therefore prepared a provisional 

 scheme, which, in order to test, I gave to the students to work with. 

 The result of a few weeks' use of this scheme convinced me that it was 

 possible so to arrange one as to make it applicable to almost any com- 

 pound, whether it was natural or artificial. I therefore drew uj) a 

 carefully-prepared scheme, which was modified from time to time, as 

 changes were suggested by its use in the blow i^ipe laboratory. The re- 

 sult was such that I felt no hesitancy in giving to students who had had 

 only a few weeks' practice, complex mixtures, feeling certain that they 

 would work systematically, and consequently with confidence and pleas- 

 ure, where they were formerly in doubt. This scheme has been in con- 

 stant use for four years, and has effected an entire revolution in the 

 working of the blow-pipe laboratory. Much of the success which has 

 attended its use is owing to the publication of a translation of Piatt- 

 uer's Manual of Blow-pipe Analysis, by Professor Cornwall,* to which 

 constant reference is made in the scheme. I have to acknowledge in 

 its preparation the valuable suggestions of my two former assistants, 

 Mr. J. H. Caswell and Professor H. B. Cornwall. 



With regard to the use of the scheme, the routine to be followed may 

 be varied according to circumstances. If sulphides, arsenides, &c., are 



'Plattner's Manual of Qualitative and Quantitative Analyses with the Blow-Pipe. 

 Translated by Professor Cornwall. 2d edition, D. Van Nostrand, New Yoik, 1873. 



