File:Official and provisional methods of analysis (1912) (14765944432).jpg

Identifier: officialprovisio10asso (find matches)
Title: Official and provisional methods of analysis
Year: 1912 (1910s)
Authors: Association of Official Analytical Chemists Wiley, Harvey Washington, 1844-1930, ed United States. Bureau of Chemistry
Subjects: Agriculture Analysis
Publisher: Washington, D.C. : G.P.O.

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No. 18 wire gauze to remove the extremelycoarse and through No. 30 wire gauze to remove the very fine. Prepare a largequantity of such calcium chlorid at the beginning and use this for the tubesK, M, and N. The reason for this is that the current of air must leave theweighed tubes with the same content of moisture as it entered them, whichonly can be attained if the absorbent in K and N is of the same nature andquality. Grind and sift the soda lime c for the weighed tubes in the same way. It ° Fresenius, Quantitative Analysis, 1: 449 ; 2: 308, German edition.6 J. Amer. Chem. Soc, 1896, 18 : 1. c An excellent method for the preparation of soda lime is given hy Benedict and Tower,J. Amer. Chem. Soc, 1899, 21 : 396. 21701°—Bull. 107—12 IS 172 METHODS OF ANALYSIS. should not be too dry, as it must not absorb moisture to a higher degree thancalcium chlorid. The tubes M and N should hold about 20 grams, making Mscapacity for carbon dioxid almost 1 gram and Ns capacity for moisture 0.2
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BAKING POWDER AXD BAKING CHEMICALS. 173 gram. M should, be refilled when its weight has increased 0.75 gram and Nafter an increase of 0.1 gram in weight. Use best rubber for all connections, applying a trace of castor oil as lubri-cator. For connections of the weighed tubes use rubber tubing boiled in weaklye, washed and dried. Apply also a little castor oil, which is thoroughly wipedoff again before connecting the tubing. Before using the apparatus fill H and K with carbon dioxid in order tosaturate the alkalinity of the calcium chlorid, and exhaust after several hours. (3) DETEKMIXATIOX. Weigh the tubes M and X, taking precaution that they are of the same tem-perature as the air in the balance room. Shortly before weighing open thetubes for a moment to allow equalization of air. Xote thermometer and barom-eter. Connect tubes with the apparatus and make sure that all joints aretight by closing A at the bottom, opening ail cocks, starting the aspirator, andobserving P, in which the li

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