3. The total solids must be determined by drying a weighed portion of the material, or a measured portion of its uniform turbid solution, at a temperature between 98.5° C. and 100° C. in shallow, flat-bottomed basins, which shall afterwards be dried until constant weight at the same temperature, and cooled before weighing for not less than twenty minutes in air-tight desiccators over dry calcium chloride. "Moisture" is the difference between 100 and the percentage of total solids, and "insoluble" the difference between "total solids" and "total solubles." 4. _Non-Tannins._--The solution must be detannised by shaking with chromed hide powder till no turbidity or opalescence can be produced in the clear solution by salt-gelatine solution. The chromed powder must be added in one quantity equal to 6.0-6.5 gm. of dry hide powder per 100 c.c. of the tanning solution, and must contain not less than 0.2 per cent. and not more than 1 per cent. of chromium calculated on the dry weight, and must be so washed that in a blank experiment with distilled water, not more than 5 mg. of solid residue shall be left on evaporation of 100 c.c. All water contained in the powder should be determined and allowed for as water of dilution. 5. _Preparation of Infusion_.--Such a quantity of material shall be employed as to give a solution containing as nearly as possible 4 gm. of tanning matter per litre, and not less than 3.5 or more than 4.5 gm. Liquid extracts shall be weighed in a basin or beaker and washed with boiling water into a litre flask, filled up to the mark with boiling water, and well mixed and rapidly cooled to a temperature of 17.5° C., after which it shall be accurately made up to the mark, again well mixed, and filtration at once proceeded with. Sumac and myrabolam extracts should be dissolved at a lower temperature. Solid extracts shall be dissolved by stirring in a beaker with successive quantities of boiling water, the dissolved portions being poured into a litre flask, and the undissolved being allowed to settle and treated with further portions of boiling water. After the whole of the soluble matter is dissolved, the solution is treated similarly to that of a liquid extract. Solid tanning materials, previously ground till they will pass through a sieve of sixteen meshes per square centimetre, are extracted in Koch's or Procter's extractor with 500 c.c. of water at a temperature not exceeding 50° C.; the extraction is then continued with boiling water till the filtrate amounts to 1 litre. It is desirable to allow the material to soak for some hours before commencing the percolation, which should occupy not less than three hours, so as to extract the maximum of tannin. Any remaining solubles in the material must be neglected or reported separately as "difficultly soluble" substances. The volume of liquid in the flask must, after cooling, be accurately made up to 1 litre.