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SCIENCE. 



[Vol. XXI. No. 539 



SCIENCE: 



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IRON AND ALUiMINIUM IN BONE BLACK: THEIR 

 QUANTITATIVE DETERMINATION. 



BY DB. F. G. WTECHMANN, COLUMBIA COLLEGE, NEW HORK. 



The determination of iron and aluminium in bone black has 

 thus far been commonly effected by the so-called ammonia- acetate 

 method, which, until quite recently, has also been the favorite 

 method employed for the determination of the constituents men- 

 tioned in mineral phosphates. 



As this method, however, is open to serious objections, it was 

 decided to test its accuracy, and to compare the results obtained 

 with those yielded, respectively, by the method of E. Glaser,' and 

 by the combination of Glaser's method with that of A. Stutzer,^ 

 first suggested by R. Jones ^ for the analysis of fertilizers. 



For valuable analytical work performed in this connection, the 

 writer's thanks are due his assistant, Mr. E. C. Brainerd. 



The schemes of analysis used in this investigation are minutely 

 given in the following directions : — 



Method I. Acetate of ammonia process. 



(This method is based on the solubility of calcium phosphate in 

 acetic acid, and on the insolubility of the phosphates of iron and 

 aluminium in this medium.) 



1. Powder sample. 3. Dry thoroughly. 3. Weigh out 3.0 

 grammes. 4. Dissolve in distilled water + 25 cubic centimetres 

 HCl (cone), boiling gently for one hour. 5. Filter. 6. Wash 

 residue on filter, until the wash-water no longer reacts for CI with 

 Ag NOs. 7. Add excess of Ba Cl^, boil till Ba SO^ is granular. 

 8. Filter. 9. Wash the Ba SO^ on the filter till no more reaction 

 for CI with Ag NO 3. 10. To filtrate and wash -waters combined 

 add NH4OH, until the precipitate formed begins to appear per- 

 manent. 11. Then add acetic acid to pronounced acid reaction, 

 and boil. 12. Filter. 13. Wash the precipitate well. 14. Dry, 

 ignite, weigh. 15. Regard the precipitate as Fe PO4 + Al FO4, 

 calculate to Fe^ O3 + Al^ Oj, and so report. 



Method II. Glaser's method. 



(In this process the calcium is removed from an alcoholic solu- 

 tion by means of sulphuric acid before the precipitation of the 

 iron and aluminium is effected.) 



1. Powder sample. 2. Dry thoroughly. 3. Weigh out 5 

 grammes. 4. Dissolve in distilled HjO + 80 cubic centimetres 

 H CI (cone.) -t- 10 cubic centimetres H NO3 (cone). 5. Make the 

 solution up to .500 cubic centimetres with distilled water. 6. Fil- 

 ter. 7. Of the filtrate take 100 cubic centimetres (equal to 1.00 

 gramme), place in a 250 cubic centimetre flask, add 25 cubic cen- 

 timetres Hj SO4 (cone). Shake frequently, and allow to stand 

 for five minutes. 8. Add absolute ethyl alcohol, cool, fill up to 

 the mark with alcohol, and shake well. 9. As volume contrac- 



' Zeltschrlft fiir Angewandte Chemle, 1889, p. 636. 



' Zeltschrlft fiir Angewandte Chemle, 1890, p. 43. 



s Chemiker Zeltung, 1890, p. 269. 



tion will take place, fill up to the mark repeatedly with alcohol, 

 and shake each time. Continue this filling up to the mark until 

 no more contraction takes place. 10. Allow the solution to stand 

 for 12 hours. 11. Filter. 13. Of the filtrate take 100 cubic cen- 

 timetres (= 0.4 gramme), place in a large platinum dish on a 

 water-bath, and heat until all the alcohol is removed. 13. Wash 

 the remaining solution into a beaker with 50 cubic centimetres of 

 distilled water. 14. Heat to boiling, and then remove the flame. 

 15. Add NH4OH very carefully to alkaline reaction. 16. Boil 

 until the ammonia is completely expelled. 17. Filter. 18. Wash 

 the precipitate thoroughly with boiling, distilled water. 19. 

 Dry, incinerate, weigh. 20. Regard the precipitate as Fe PO4 + 

 Al PO4, calculate to Fe^ O3 + Alj O3. and so report. 



Method III. Combination of the methods of Glaser and Stutzer. 



(Stutzer's method consists essentially in precipitating the iron 

 and aluminium, principally as phosphates, in a solution of am- 

 monium acetate; treating this precipitate with a solution of 

 ammonium molybdate, to remove the phosphoric acid as phospho- 

 ammonium molybdate; filtering out this precipitate, and in the 

 resulting filtrate precipitating the iron and aluminium as hydrates, 

 by ammonium hydrate; drying and igniting this precipitate, 

 weighing it as Fe^ O3 -1- Al^ O3, and reporting it as such.) 



The following scheme, it is believed, offers all the advantages 

 of both the Glaser and the Stutzer methods. 



Proceed exactly as in Method 11. up to and inclusive of section 

 No. 18. 



Then continue as follows: — 



1. Place filter and contents in a beaker which contains 

 150 cubic centimetres molvbdic solution,* at a temperature of 

 about 40° C. 3. Keep the mixture at a temperature of about 

 65° C. for from 12 to 15 hours. 3. Filter out the precipitate. 

 4. Wash the precipitate thoroughly with NH4 NOj solution. 

 (1:10). 5. To filtrate add NH4 OH till it is well alkaline. 



6. Heat for 2 or 3 hours over a gentle flame, replacing any loss 

 by evaporation by the addition of water and ammonic hydrate. 



7. Filter out the precipitate. 8. Dissolve this precipitate from 

 the filter with H CL 9. Precipitate with NH4OB, and boil out all 

 free ammonia. 10. Filter. 11. Wash precipitate, dry, incinerate, 

 and weigh. 12. Regard the precipitate as Fe^ O3 4- AI2 O3, and 

 so report. 



The mixture on which these three methods were tested con- 

 sisted of: — 



Tri-calcic phosphate 20.00 grammes 



Aluminium sulphate 0.10 '• 



Ferrous sulphate 0.10 " 



These amounts of the sulphates of iron and aluminium corre- 

 sponded to 0.67 per cent of Fe^ O3 -f- Alj O3, as was ascertained 

 by analysis. 



The mixture was dissolved in H2 O -i- H CI, and made up to 500 

 cubic centimetres. 24.75 cubic centimetres of this solution con- 

 tain 1.00 gramme of the dry substance. 



In Method I., used 3.00 grammes ; in Method II., 1.00 gramme; 

 in Method III., used 1.00 gramme of the "dry substance" for 

 analysis. 



Results of Analysis. 



Method. 



Method I. has evidently yielded the least satisfactory result. 



*> Dissolve 100 grammes molybdlc acid in 40 grammes, or 417 cubic centi- 

 metres of ammonium hydrate (sp. gr. 0.961, and pour the solution thus ob- 

 tained into 1500 grammes, or 1250 cubic centimetres, of nitric acid (sp. gr. 

 1.20). Keep in a warm place for several days, decant the solution from any 

 sediment, and preserve in glass-stoppered vessel. 



