THE CHEMICAL NEWS. VOLUME XXXV. EDITED BY WILLIAM CROOKES, F.R.S., &c. ON THE No. 893.-JANUARY 5, 1877. ESTIMATION OF PHOSPHORUS IN THE FORM By SERGIUS KERN, St. Petersburg. EGGERTZ gives in his Swedish work, "Om Kemisk, profning af Tern, Ternmalmer, och Braennmaterialier," a method of quantitative analysis of phosphorus which is based on the precipitation of phosphorus in the form of phospho-ammonio-molybdic salt by a mixture called "molybdic solution," prepared by dissolving 100 grms. of molybdic acid in 422 c.c. of ammonia, o'95 specific gravity, and mixing this solution with 1250 c.c. of nitric acid, 1.20 specific gravity. This method he employed in analyses of iron and steel, and since then a great many analyses have been executed by this method in laboratories of iron works. Working now almost entirely with products of such works, and analysing Bessemer and crucible steels for phosphorus, I find that the method as designed by Eggertz must be altered in details. The author of this method advises to proceed as follows for the quantitative analysis of phosphorus: I grm. of the iron specimen is dissolved in 12 c.c. of nitric acid; the liquor is next evaporated on a sand-bath to dryness; the residue is dissolved in 5 c.c. of aqua regia, and to the solution 4 c.c. of water is added. The liquor is filtered from the silica; the filtrate must not be more than 20 c.c. From this solution the phosphorus is precipitated by about 30 c.c. of molybdic liquor, the preparation of which has been already mentioned. The solution is left for 15 hours in a warm place, and is then filtered. The precipitate containing phosphorus is washed by cold water acidulated with one per cent. of nitric acid. The yellow precipitate is dried on the filter at 100° in an air-bath and weighed. This precipitate contains 1.63 per cent. of phosphorus. On this process I wish to make some remarks-practical remarks, I had better say. 1. For dissolving iron it is better to use aqua regia, because nitric acid is not such a powerful agent for decomposing the whole of the organic matter which is often found in irons; the presence of this was found to prevent the precipitation of phosphorus by the molybdic solution. 2. The process of filtration and washing of the yellow precipitate must be executed very rapidly, because other wise a certain quantity of the yellow precipitate is dissolved, and passes through the filter with the solution. Many trials were made, and it was always found that a small quantity of the precipitate passed into solution. In this case a lower percentage of phosphorus is obtained; this gives incorrect results in analysing steels and irons, and such materials where a small amount of phosphorus not estimated may give faulty results in the classification of the materials. 3. Eggertz advises to wash the yellow precipitate with water acidulated by nitric acid, and dry it on the filter at 100°. In practice this operation is nearly impossible, firstly because the precipitate is slightly soluble in acidulated water, secondly because a small quantity of the acid always remains on the filter, from which the filter when dried is always a little rotten; this fact also influences the percentage of phosphorus calculated. The best method was found to be the following: I grm. of the specimen is dissolved in 20 c.c. of aqua regia, and the phosphorus is precipitated by Eggertz's the solution, is dissolved on the filter in ammonia, and in method; the resulting yellow precipitate, separated from the filtrate obtained, slightly acidulated by hydrochloric acid, the phosphorus is precipitated in the form of phospho-ammonio magnesic salt [Mg(NH4)PO4] by "magnesium mixture," prepared by dissolving 1 grm. of MgSO4 and 1 grm. of NH4Cl in 8 c.c. of water mixed with 4 c.c. of ammonia. The precipitation is finished in 15 to 20 hours; the precipitate is filtered from the soluof ammonia, and first gently heated in a platinum crution, washed with water containing half a per cent. cible till free NH3 and H2O are evaporated; the crucible next is ignited for 30 to 40 minutes, and the received This salt contains 13:51 per cent. Mg2P2O is weighed. of phosphorus. This combination of Eggertz's method with the old one gives very exact results in analyses of irons and steels. See vol 261 255 Obouchoff Steel Works, St. Petersburg. NEW APPLICATIONS OF GLYCERIN IN THE By A. H. CHURCH, M.A. FOR some time past I have used glycerin for preventing the adhesion of vulcanised india-rubber tubing to the inlet pipes of Bunsen and other gas-burners. A drop or two smeared on the parts in contact prevents both surfaces from suffering those changes which give rise to such continued annoyance in the laboratory. The glycerin should be pure. One of the most serious drawbacks to the use of paraffin lamps for microscopic and other purposes is the perpetual creeping out of some of the hydrocarbon through the cement wherewith the metal burner is fixed to the glass reservoir. If this cement be soaked with glycerin before oil of any kind be introduced into the lamp this annoyance does not occur. |