Chemistry and Physics. 79 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. A Quantitative Reagent for Iron and Copper, — In recent 

 years various organic products have come into use as reagents 

 for precipitating metals in quantitative analysis. One of the 

 latest of these is nitroso-phenyl-hydroxylamine, C„HjN(NO)OH, 

 introduced by Baudisch for the precipitation of ferric iron and 

 copper. The ammonium salt of this base is an article of com- 

 merce under the name " Kupferron." Biltz and Hodtkk have 

 put the reagent to test and have obtained very satisfactory 

 results. In the precipitation of iron a large amount of acid, 

 either hydrochloric, sulphuric or acetic, may be present ; even 

 20"'' of concentrated hydrochloric acid in 100°'^ of solution does 

 no harm. The reagent was used in 6 per cent solution, being 

 added at room temperature with stirring. The end of the pre- 

 cipitation is readily observed by the formation of a white pi-ecipi- 

 tate of the base itself following the reddish brown iron precipitate. 

 It is recommended to use an excess of about a fifth of the reagent. 

 After 15-20 minutes the precipitate may be filtered on paper, 

 preferably with suction, washed with water at room temperature 

 until the acid is removed, then with strongly ammoniacal water 

 to remove the excess of reagent, and then again with water. The 

 ignition requires some care to prevent loss. Excellent results 

 were obtained in this way in the determination of iron in the 

 presence of aluminium, nickel, and chromium, where in extreme 

 cases as much as 50 parts of each of these metals to 1 part of 

 iron were present. The fact that these separations can be made 

 makes the method a valuable one. 



For the determination of copper with this reagent a lai'ge 

 excess of mineral acid is to be avoided, and acetic acid appears to 

 be best. Otherwise the operation is the same as for ierric iron, 

 except that the excess of reagent was removed with 1 per cent 

 sodium carbonate solution. Good results were obtained in sepa- 

 rating copper from 10 parts of zinc using acetic acid solution, 

 but for the separation of copper from cadmium it was found 

 necessary to use dilute mineral acid solution. Attempts to sepa- 

 rate iron and copper by precipitating both together and dissolv- 

 ing out the copper compound on the filter with ammonia gave 

 slightly high results for the iron. 



As far as the experiments have gone, it appears that iron and 

 copper cannot be separated from silver, mercury, lead or tin, as 

 these metals are also precipitated. — Zeitschr. anorg. Chem., Ixvi, 

 426. ' H. L. w. 



2. The Detection and Determination of Very Minute Quanti- 

 ties of Silver. — The estimation of very small quantities of silver 

 is of importance particularly in connection with atomic weight 



