Determine and report insoluble matter, aluminium oxide (Al_{2}O_{3}), ferric oxide (Fe_{2}O_{3}), ferrous oxide (FeO), basicity ratio, and, if present, free acid as H_{2}SO_{4}. If the material is what is known as “granular” sulfate mix it well before sampling. If it is in lump form crush it to ⅛ to ¼ inch size, mix, and sample it. It is unnecessary to grind the sample to a fine powder, but it is preferable to have the particles fairly uniform in size. INSOLUBLE MATTER. Treat 10 grams of the sample with 100 cc. of distilled water and digest one hour at boiling temperature. Filter through a weighed Gooch crucible and wash the insoluble matter with hot water freshly boiled to free it from carbon dioxide. Dry the crucible to constant weight at 100° C., cool, and weigh. Report the percentage of insoluble matter. OXIDES OF IRON AND ALUMINIUM. Dilute the filtrate from the determination of insoluble matter to 500 cc. with water free from carbon dioxide and thoroughly mix the solution. Transfer 50 cc. of the solution to a 250 cc. beaker, add about 150 cc. of water and 5 cc. of concentrated hydrochloric acid, and heat to boiling. Add ammonium hydroxide in slight excess; when the solution has been almost neutralized it is convenient to add a drop of methyl orange indicator and then to add about 0.5 cc. of ammonium hydroxide after the solution is neutral to the indicator. Digest at about 100° C. for a few minutes and filter. Some analysts prefer to wash this gelatinous precipitate with hot water by decantation, and some to wash it evenly distributed over the surface of a filter paper; either method may be used. It is difficult to free it completely from impurities and it is not necessary to do so unless unusual quantities of calcium, magnesium, sodium, or potassium are present. While the precipitate is being washed do not allow it to become dry, as it then packs and can not be washed clean. After most of the water has drained drying the filter may be hastened by placing it on a sheet of blotting paper. If much iron is present completely dry the precipitate, remove it from the paper, and ignite the paper separately. Finally, blast the precipitate, with free access of air to the crucible, for five or ten minutes, cool, and weigh as oxides of iron and aluminium (Fe_{2}O_{3} + Al_{2}O_{3}). Subtract the content of total iron, expressed as ferric oxide (Fe_{2}O_{3}), from the weight of the combined oxides and report the difference as aluminium oxide (Al_{2}O_{3}), in percentage. TOTAL IRON.