SCIENCE. 



569 



SCIENCE: 



A Weekly Record of Scientific 

 Progress. 



JOHN MICHELS, Editor. 



TERMS: 



Per Year, - • - - - Four Dollars 

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 TRIBUNE BUILDING, NEW YORK. 



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SATURDAY, DECEMBER 3, 1881. 



SUGAR ANALYSIS* 



This is an admirable manual of sugar analysis, and 

 will prove a great boon to everyone engaged in sugar 

 work. The resume of the chemistry of the sugars 

 with which the book opens is of especial value to the 

 student who wishes to get a clear idea of this compli- 

 cated subject. Perhaps it had been desirable to have 

 had the book delayed a little longer in order to have 

 incorporated the results of the last year's study in 

 sugar analysis, but this objection would obtain equally 

 against any book published at any time. Another 

 valuable feature of the book is its collection of tables 

 referring to all conditions of sugar analysis, viz. 

 specific gravities, solubilities, etc. The author is 

 careful to cite authorities for his statements, and thus 

 anyone wishing to pursue any given topic further can 

 readily do so without being at the trouble of hunting 

 up each theme for himself. 



There is, however, a vast mass of French and 

 German literature on certain sugar compounds which 

 might be very appropriately drawn upon in an exhaus- 

 tive study of the chemistry of sugar, and which is of 

 no use whatever to the analyst. There is much of 

 this in the book before us, and while it detracts noth- 

 ing from its merit as a help to the analyst, it certainly 

 adds nothing to it. 



That portion of the work which is devoted to the 

 description of the optical examination of sugars is to 

 be highly recommended. We have, however, used 

 for three years a Schmidt & Hansen polariscope, and 

 were therefore a little startled to read " ordinary lamp 

 light, and not the monochromatic flame, is required." 



We doubt very much whether, in testing the accu- 

 racy of the scale of a polariscope, quartz plates of vari- 



* Manual of Sugat Analysis, by J. H. Tucker, Ph. D., Van Nostrand, 

 New York, 1881. 



ous thicknesses are better than solutions of pure 

 sugar. First of all, the plates themselves would have 

 to be tested, and this would require as much work 

 and trouble as testing the scale directly with sugar 

 solutions. If quartz plates could be secured which 

 were absolutely accurate, of course this objection 

 would not occur. 



Among the sources of monochromatic light the 

 author omitted to mention the new double burner of 

 Laurent, which leaves nothing to be desired in the 

 steadiness and intensity of the sodium flame. 



There is one statement which the author makes in 

 a note (p. 137) on Clerget's method of analysis that 

 seems calculated to mislead. It is : " it must be re- 

 membered that the process is entirely inapplicable 

 when any optically active body is present besides cane 

 or invert sugar, and also if the invert sugar 

 itself exists in an inactive condition as regards 

 polarized light." In point of fact, any opti- 

 cally active body may be present without rendering 

 the process inapplicable, provided it is not affected by 

 the process of inversion. Thus, by Clerget's method 

 we can accurately determine cane sugar in the pres- 

 ence of dextrose, maltose and glucose. In polarizing 

 an inverted cane sugar, too, metal tubes should be 

 used, since the temperature is more accurately ob- 

 tained from an external thermometer than in a glass 

 tube. 



The author's directions for estimation of raw sugar 

 and syrups are those which are generally recommended 

 and employed. The description of these methods is 

 full and admirably arranged. In fact, this praise can 

 be bestowed on every part of the work. The only 

 trouble about the methods is that if applied to the 

 ordinary syrups of commerce they will give the most 

 alarming errors. 



The great fault of the work, in fact, is found in its 

 failure to give reliable methods for the examination of 

 the mixed sugars and syrups which are on the market 

 to-day. 



Perhaps, however, we should not say this is a fault 

 of the book, it is rather a fault of science. To deter- 

 mine cane sugar, invert cane sugar, dextrose, dextrine, 

 and maltose exactly, is a great problem which the 

 author leaves untouched and which demands the care- 

 ful attention of sugar chemists. 



In papers read before the A. A. A. S., at the Boston 

 and Cincinnati meetings, and published in the pro- 

 ceedings for the Boston meeting and in this Journal, 

 Nos. 65 and 66, Prof. Wiley has shown the relation 

 between rotating and reducing power in commercial 

 starch sugars and also a series of determinations of 

 cane sugar in mixed sugars. 



Since the polariscope has grown to be the chief in- 

 strument in sugar analysis and starch sugars and 

 syrups a common article of commerce and consump- 

 tion the omission of any reference to those papers is 

 a matter to be regretted. 



