Experiment Station Record, Volume 19, 1907-1908 Page: 8
xx, 1316 p. ; 24 cm.View a full description of this book.
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8 EXPERIMENT STATION RECORD.
vegetable proteids are hygroscopic, so it is almost impossible to use anhydrous
material for analytical purposes. Accurate determinations of the water content
are therefore essential in reporting analyses.
"The usual custom of investigators has been to determine the moisture by
beating in an air bath at 110 C., and as the results in this paper show, the
determinations thus made may readily be subject to an error of 1 per cent.
Obviously an error of 1 per cent or more in the water determinations would
result in an error of one-half of 1 per cent in the carbon determinations, and a
measurable error in the determination of nitrogen. It can only be said that in
the majority of researches on the animal or vegetable proteins, the carbon and
nitrogen determinations are in large measure only used for comparative observations,
and hence the absolute nitrogen or carbon content is not of as great
importance. It is clear, however, that at least so far as the materials used
in these investigations are concerned, it is impossible to determine the moisture
content in them by drying in hot air at a temperature of 100 to 110.
"The removal of the final traces of moisture which are persistently retained
by the proteins when dried in an air bath at a temperature of 110 can be
effected by subsequent desiccation in a high vacuum for 2 weeks."
The detection and estimation of reducing sugars, S. R. BENEDICT (Jour.
Biol. Chem., 3 (1907), No. 2, pp. 101-117).-From a study of methods of estimating
sugar, the author recommends a copper-carbonate solution and gives
directions for its preparation. For delicate work in sugar detection, either in
pure solutions or in urine, the reagent should be freshly mixed and diluted.
The method outlined for the volumetric estimation of sugar requires a solution
of crystallized copper sulphate in water, a solution of crystallized Rochelle
salt with pure anhydrous sodium carbonate, and a solution of potassium sulphocyanid.
"For use these solutions are mixed in equal proportions in the
order indicated. To every 30 cc. of the solution thus obtained are added from
2.5 to 5 gm. of pure anhydrous sodium carbonate. The amount of this substance
added should roughly correspond to the dilution to which the solution will be
subjected during the titration, i. e., for titrating dilute sugar solutions add
greater quantity of carbonate and vice versa. The solutions are mixed in a
beaker of suitable capacity, the requisite quantity of carbonate added, and the
mixture heated to boiling over a gauze until the carbonate completely dissolves.
Thirty cc. of this mixture (equivalent to 10 cc. copper sulphate solution) are
equal to approximately 0.073 gm. of pure dextrose.
"'The titration is carried out as follows: The sugar solution is run in from a
burette rather rapidly (not so rapidly as to interfere markedly with continuous
vigorous boiling) until a heavy, chalk-white precipitate is formed and the color
of the fluid begins to lessen perceptibly. The last portions should be run in in
quantities of from 2 to 10 drops (depending on depth of color remaining and
the relative strength of the sugar solution), with a vigorous boiling of about
one-fourth minute between each addition. The end point of the reaction is the
complete disappearance of the blue color. This point is sharp and satisfactory.
The precipitate obtained is chalk-white and is rather an aid than a hindrance
to the determination of the end point."
Separating starch and- glycogen, E. BAUR and E. POLENSKE (Arb. K. Gsndhtsaint.,
24 (1906), No. 3, pp. 576-580; abs. in Zentbl. Gesam. Physiol. u. Path.
Stoffwechsels, n. ser., 2 (1907), No. 2, p. 79).-In the examination of sausage a
method of separating starch and glycogen is desirable, and that elaborated by
the author depends upon the fact that glycogen is soluble in a saturated solution
of ammonium sulphate, while starch is not. After filtration and dilution the
glycogen is precipitated with alcohol. Comparative tests showed that the
method gave satisfactory results.
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General Index to Experiment Station Record Volumes 13-25, 1901-1911 (Book)
A topical, alphabetically arranged index to volumes 13-25 including experiment station records, publications reviewed, and foreign publications. In has a 'Consolidated Table of Contents' which lists all editorial notes and publications of the experiment stations and Department of Agriculture from the referenced volumes
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United States. Office of Experiment Stations. Experiment Station Record, Volume 19, 1907-1908, book, 1908; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc5035/m1/28/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.