16 



IX. 'Methods of Estimation of Carbohydrates III. The 

 Cupric Reducing Poxver of the Pentoses — Xylose and 

 Arabinose." A. J. DAISH. Journal of Agricultural 

 Science, 1914. 6, 255—262. 



In the scheme of analysis of plant extracts outlined in last year's 

 report (1913, pp. 12-14) allowance must be made for the pentoses 

 present ; it therefore became necessary to ascertain the exact value 

 of the cupric reducing power under the standard conditions of 

 Brown, Morris, and Millar. Pure specimens of the xylose and 

 arabinose were therefore prepared and the reducing power at different 

 degrees of concentration accurately determined. The results are 

 given in tables and curves, enabling one to read off directly the 

 weight of pentose corresponding to different weights of cupric 

 oxide. The specific reducing power of the pentoses differs only 

 very slightly from that of dextrose. 



X. • "The Estimation of Carbohydrates IV. The Presence 



of Free Pentoses in Plant Extracts and the Influence 

 of other Sugars on their Estimation." W. A. DAVIS 

 and G. C. SAWYER. Journal of Agricultural Science, 

 1914. 6,406—412. 



The existence of free pentoses in plants has not hitherto been 

 recognised. Evidence is adduced to show that they are usually 

 present in the alcoholic extracts of leaves of turnips, mangolds, 

 potatoes and other plants. This also explains their accumulation in 

 the "vinasses" of distilleries employing the molasses of the beet 

 sugar industry. 



It is shown that the pentoses may be estimated quantitatively 

 with a fair degree of accuracy by the ordinary distillation process or 

 from the reducing power of the purified liquor after other sugars 

 have been fermented away with yeast. 



When the amounts of pentoses are small, relative to the other 

 sugars, it is advisable, as suggested by Kluyver, to ferment away 

 these sugars completely before applying Krober's process. 



XI. The Hydrolysis of Maltose by Hydrochloric Acid under 

 the Herzfeld Conditions of Inversion." W. A. DAVIS. 

 Journal of Agricultural Science, 1914. 6, 413 — 416. 



It is shown that maltose undergoes slight hydrolysis (about 

 2 per cent, when 1 per cent, solutions of maltose are employed) 

 when heated with hydrochloric acid under the Herzfeld conditions 

 of inverting cane sugar. It is preferable, therefore, to adopt 10 per 

 cent, citric acid as suggested in last year's report, as this acid causes 

 no hydrolysis of maltose under the conditions prescribed. 



XII. "Estimation of the Surface of Soils." J. A. Hanley. 



Journal of Agricultural Science, 1914. 6, 58 — 62. 



The method of Konig, Hasenbaumer, and Hassler for estima- 

 ting soil colloids by means of dyes was considerably modified. 



Methyl violet was used, as this colour undergoes only a slight 

 change even after prolonged contact with the soil ; but it was shown 

 to be useless to employ dye solutions of the same strength for soils 

 of the same type, e.g., for sands, 1 gram ; for loams, 2 grams ; for 

 clays, 3 grams of dye per litre. 



