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The estimation of carbohydrates. V. The supposed precipitation of reducing sugars by basic lead acetate

Published online by Cambridge University Press:  27 March 2009

William A. Davis
William A. Davis
Affiliation:
(Rothamsted Experimental Station).
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Extract

Gill in 1871 first pointed out that when an excess of basic lead acetate is added to a solution of invert sugar the negative rotation of the latter is greatly reduced owing to the formation of a soluble lead compound of laevulose. If sufficient lead solution is added the negative rotation may become a positive one; thus in one experiment quoted by Gill a negative reading of – 28° was transformed into a positive value of + 57°. The change of rotation was not, however, permanent and on removing the lead or on acidifying the solution the original rotatory power was restored. The change of rotation was attributed to an effect of the lead on the laevulose only; a solution of dextrose was practically unaffected by the presence of basic lead acetate. Since Gill's paper the effect of basic lead acetate as a source of error in sugar analysis has been the subject of numerous papers especially by Pellet, Svoboda, Edson, Prinsen Geerligs, Watts and Tempany and Eynon.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 8 , Issue 1 , September 1916 , pp. 7 - 15
Copyright
Copyright © Cambridge University Press 1916

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References

Page 7 note 1 Trans. Chem. Soc. 1871, 24, 91.Google Scholar

Page 7 note 2 Bull. Assoc. Chim. Sucr. 1891, 9, 439Google Scholar; 1896, 14, 28 and 131; 1897, 15, 605; 1899, 16, 1007 and 1147; 1900, 17, 52; 1904, 22, 744; 1913, 31, 205; 1914, 32, 909. J. Fabr. Sucr. 1899, 40, No. 15.Google ScholarSucrerie Indigene, 1904, 64, 67.Google Scholar

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Page 8 note 1 For example by von Lippmann, in Lunge's Chem. Techn. Untersuch. Methoden, 3, 485 (5th Ed.)Google Scholar: by Ling (Thorpe's Dict. App. Chem. article “Sugar,” p. 244). Compare also Allen's, Commercial Organic Analysis, 4th Ed., 1, 311.Google Scholar

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Page 9 note 2 Pellet, , Bull. Assoc. Chim. 1899, 16, 1181Google Scholar and 1902, 19, 834.

Page 9 note 3 It is usually quite easy by testing small portions of the filtrate to hit off the point at which this occurs to within 1 or 2 c.c, even when relatively large quantities (for example, 200 to 300 c.c.) of the basic lead solution have to be used.

Page 10 note 1 If the solution is to be kept for any time a little toluene should be added and the mixture well shaken. If sodium carbonate is used any large excess should be avoided, tests being made during the precipitation until exactly the right quantity has been added. When these precautions are observed the solution can be kept for months without any change, even inversion of saccharose, taking place.

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Page 10 note 3 Sucrerie Beige, 1912, 275.

Page 11 note 1 Davis, and Daish, , This Journal, 1914, 5, 454.Google ScholarPubMed

Page 11 note 2 This Journal, 1914, 6, 152.Google ScholarPubMed

Page 12 note 1 Trans. Chem. Soc. 1897, 71, 72.Google Scholar