The Mexican mining journal . with the mixture of one part strong ammoniaand one part hydrogen peroxide, allowing it to run throughinto the beaker containing the rest of the the solution to effect complete solution and oxi-dation of the arsenious sulphide, filter if necessary,and boil down to 10 to 20 Cool, and add 10 ammonia. Cool, and add gradually 5 to 10 mixture, stirring continually for about 5minutes; and allow to stand over night. The precipitated ammonium magnesium arsenate isfiltered off through a previously ignited and weighedalundum filt
The Mexican mining journal . with the mixture of one part strong ammoniaand one part hydrogen peroxide, allowing it to run throughinto the beaker containing the rest of the the solution to effect complete solution and oxi-dation of the arsenious sulphide, filter if necessary,and boil down to 10 to 20 Cool, and add 10 ammonia. Cool, and add gradually 5 to 10 mixture, stirring continually for about 5minutes; and allow to stand over night. The precipitated ammonium magnesium arsenate isfiltered off through a previously ignited and weighedalundum filtering crucible, and washed three timeswith ammonia water (3 parts water to 1 part am-monia). Dry in water oven and ignite over the blow-pipe for 10 minutes, cool, and weigh as ^Oj. The tartaric acid solution is made by dissolving 400gm. tartaric acid in 400 water, and adding 400 nitric acid. Magnesia mixture:—Take 110 gm. magnesiumchloride and 140 gm. ammonium chloride and dissolvein 1,300 Rosario, Chih. Assay of Tin Ores and Concentrates. Summary of Vicivs on the Pearce-Lou) Assay. 1. The degree of fineness of the ore must be at least100 mesh, otherwise a representative sample cannotbe obtained. 2. Nickel crucibles are superior to iron ones; thetime of reduction is not so long if nickel crucibles areused for fusion. For tailings, fusion in an iron crucibleshould be avoided; it is desirable to keep the amountof ferrous chloride in the solution as low as possible,particulary when the tin contents is small, otherwisehigh results are obtained. 3. The amount of hydrochloric acid should be aboi:125 cc. 4. The bulk of the solution before reduction shouldbe about 400 cc 5. The temperature of the tin solution at titrationshould not be more than 700 F. 6. The strength of the standard solution should notgenerally be more than 11 gm. of iodine and 20 potassium iodine per litre, or less than one-thirdthe above strength. 7. Before titration the calc
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