Leather Chemists' Pocket-book: A Short Compendium of Analytical Methods

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E. & F.N. Spon, Limited, 1912 - Leather - 223 pages
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Page 84 - ... to filter a portion of the tanning solution through the Berkefeld candle till optically clear, which can generally be accomplished by rejecting 300 or 400 cc and returning the remaining filtrate repeatedly ; and at the same time to evaporate 50 cc of clear filtrate obtained by the method for which correction is required, when the difference between the residues will be the correction sought Note.
Page 85 - The moisture in the air-dried powder is determined, and the quantity equal to 6'5 grammes actual dry hide-powder is calculated, which will be practically constant if the powder be kept in an air-tight vessel. Any multiple of this quantity is taken according to the number of analyses to be made, and wet back with approximately ten times its weight of distilled water.
Page 85 - ... of water, and must be sufficiently free from soluble organic matter to render it possible in the ordinary washing to reduce the total solubles in a blank experiment with distilled water below 5 mgr. per 100 cc The powder when sent out from the makers shall not contain more than 14 per cent. of moisture, and shall be sent out in air-tight tins.
Page 82 - Sumach and myrobalans 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...
Page 83 - A further portion is now filtered in the exact method for which the correction is required (time of contact and volume rejected being kept as constant as possible) and 50 cc is evaporated to determine
Page 81 - ... of solid residue shall be left on evaporation of 100 cc All water contained in the powder should be determined and allowed for as water of dilution.
Page 100 - All evaporations and dryings shall be conducted in the form of apparatus known as the "Combined Evaporator and Dryer," at a temperature not less than 98° C.
Page 86 - Of this solution 20 cc. per 100 gms. or 1'3 cc. per 6'5 gms. of dry powder should be used. At the end of one hour the powder is squeezed in linen to free it as far as possible from the residual liquor, and washed and squeezed repeatedly with distilled water, until on adding to 50 cc.
Page 83 - ... hours, so as to extract the maximum of tannin. Any remaining solubles in the material must be neglected, or reported separately as " difficultly soluble
Page 80 - The total solubles must be determined by the evaporation of a measured quantity of the solution previously filtered till optically clear both by reflected and transmitted light ; that is, a bright object such as an electric light filament must be distinctly visible through at least 5 cm. thickness, and a layer of 1 cm. deep in a beaker, placed in a good light on black glass or black glazed paper, must appear dark and free from opalescence when viewed from above.

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