4:06 Dr. Brett on detecting minute quantities 



One out of the eight parts just referred to was fused with 

 500 grs. of zinc, and 150 grs. of this alloy were placed in the 

 apparatus ; several distinct antimonial stains were obtained : 

 the proportion of antimony to zinc in this case was as 1 to 

 11,000. 



One out of the eight parts was fused with 600 grs. of zinc ; 

 150 grs. of the alloy yielded in the apparatus a very few 

 small but sufficiently characteristic antimonial stains : the pro- 

 portion of antimony to zinc in this case was as 1 to 13,000. 

 This appeared to be the minimum quantity which could be 

 satisfactorily detected in an alloy of zinc and antimony. I 

 then proceeded to ascertain the minimum quantity of anti- 

 mony which could be detected by these means ; in the form 

 of sesquioxide of antimony well crystallized tartar emetic 

 was used. 



5'24? grs. of transparent well crystallized tartar emetic equal 

 to 2*23 grs. of sesquioxide of antimony = 1'88 metallic anti- 

 mony, were dissolved in 60 measures of water. 



Half a measure placed in the hydrogen apparatus gave 

 very distinct antimonial stains ; the quantity of metal in this 

 case was = *0156 gr. 



One-third of a measure under similar circumstances gave 

 distinct stains, small in size, and approximating in appear- 

 ance arsenical stains : the quantity of metal in this case was 

 = 'OlOM gr. 



One-sixth of a measure under analogous circumstances 

 gave stains very small, and two or three only in number : the 

 quantity of metal in this case was = '00522 gr. This ap- 

 peared to be the minimum quantity capable of being detected 

 by such means. 



The colour of the flame when antimony is present in quan- 

 tity sufficient to produce large and dark stains does not differ 

 materially from that observed when arsenic is present, both 

 possessing a bluish tint, more distinct, however, in the case of 

 arsenic ; very small quantities of arsenic render the flame blue, 

 but when the quantities of antimony approach the minimum 

 the blue colour is not observable. The mere hydrogen flame 

 becomes considerably enlarged, especially when arsenic is 

 added to the apparatus, and the disengagement of gas bubbles 

 in the generating vessel becomes more active. The same 

 phsenomena may be noticed when antimony is present, but 

 not in so remarkable a degree. I have many times had oc- 

 casion to observe that when very minute quantities of arsenic 

 or antimony are present, that metallic stains are not sometimes 

 made fianifest upon white porcelain until the lapse of some 

 minutes; it is of importance to be aware of this circumstance, 



