138 Proceedings of Indiana Academy of Science 



tube. Add .l-.2g-. 30-mesh aluminium. Warm the solution and shake it 

 while the metal is going into solution so as to insure contact of the 

 metal with all parts of the solution. Continue to heat until all gas- 

 evolution has ceased so as to avoid carrying over tin with the precipitated 

 antimony. Let the black antimony settle to the bottom of the tube and 

 decant the liquid through a filter into a tube containing some mercuric 

 chloride solution. A white precipitate, which may turn gray, proves the 

 presence of tin. 



Wash the black precipitate in the tube with hot 12N HCl and with 

 water to remove traces of tin. This may be done by decantation. Cover 

 with See. HCl, add a few drops of nitric and bcil to destroy the aqua 

 regia. Dilute to about 20cc. and pass in hydrogen sulphide. An orange 

 precipitate proves the presence of antimony. 



The writer wishes to thank his student, Mr. Merrell Fenske, for 

 the aid he has given in working out this problem. 



QUALITATIVE ANALYSIS— IRON GROUP. 



Ralph W. Hufferd, DePauw University. 



Careful examination of the results obtained by several classes in 

 Qualitative Analysis has led the writer to the belief that no other 

 group causes .so much trouble or consumes so much of the students' 

 time as does the Iron Group. Further study has brought out the fact 

 that the most commonly mis.^ed members of this group are cobalt and 

 zinc. The difficulty with the first of these seems to be due to faulty 

 application of the potassium cobaltinitrite test, and with the second, to 

 failure to extract zinc from the group precipitate and the reluctance 

 of the average student to seek for it in the second division precipitate. 



Investigation of the various tests for nickel led the writer to attempt 

 a modification of the old Morrel-Vogel test. The results in this direction 

 vi^ere quite satisfactory and pointed to the possibility of greatly simpli- 

 fying the scheme of analysis of the whole division. 



Attention was then directed toward the zinc problem. If zinc 

 could be satisfactorily separated from the second division, the neces- 

 sity for the very annoying and time-consuming second precipitation and 

 filtration of cobalt and nickel sulphides would be avoided. This notwith- 

 standing contrary belief on the part of certain authors, was found to 

 be quite satisfactorily accomplished by using a large excess of sodium 

 hydroxide in separating the two divisions. (It must be noted that this 

 procedure may increase the quantity of silicic acid in solution, though 

 in no case has there been evidence of nickel being present in the zinc 

 sulphide precipitate.) There is no desire on the part of the writer 

 to deny that small quantities of zinc may be carried over in the second 

 group precipitate but he does hold that except in very extraordinary 

 cases it is unnecessary to look for it as the greater part of it will show 

 up in the proper place. 



Several other slight deviations from the moi-e commonly accepted 

 methods will be noticed in a .study of the revised method which follows. 

 They are all in the direction of speeding up the process without lessening 

 its accuracy. 



