Bulletin - United States. Bureau of Soils Volume 11-26 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1898 Excerpt: ... long time to expel carbon dioxide. The results are presented in tables XXIII, XXIV, XXV, and XXVI. Those given in Table XXIII were obtained by an assistant, in the laboratory, who had had no previous experience with the method; titrations Nos. 1 and 2, made in beakers, being intended merely as rough determinations to familiarize him with the method. The other titrations were made in porcelain dishes. No titrations whatever have been discarded, all being presented as they were obtained and without preference. The methyl orange for all the titrations in which its use is described in this paper was prepared by dissolving 1 gram in 200 cubic centimeters of water. A single drop only was used for a titration. Even smaller quantities would have been preferable. The Congo red was prepared by making a saturated solution in 30 percent alcohol. The first column of the table gives the number of the experiment; the second column, the number of cubic centimeters of the sodium carbonate solution; the other columns, the number of cubic centimeters of the hydrogen potassium sulphate solution required, the indicator used being stated at the head of the column: Table XXIII.--Titrations of Xa, CO, solution unth N/'0 HKSO, for the purpose of comparing methyl orange and Congo red as indicators. A series of titrations was then made to determine at what point the titration should cease after the color change began. It was clearly demonstrated that the best procedure was to titrate until no further change of color could te observed--in striking contrast to what was found advisable when methyl orange was used. This point established, the titrations presented in Table XXIV were made, the statement in brackets at the right referring to the amounts of indicator used. The titrations wer...