§§ 198, 199. COMPOSITION AND ESTIMATION. 213 



inactive ; sinistrin and triticin ^ differ from one another in the 

 extent to which they deviate a ray of polarized light. Triticin 

 reduces Fehling's solution rapidly, Ijut levulin and sinistrin require 

 long boiling before cuprous oxide separates out (levulin, H hour). 

 These three carbohydrates also differ in the rapidity with which 

 they are converted into glucose when heated with pure water in 

 sealed tubes. Triticin is here the first to undergo a partial trans- 

 formation into sugar. Levulin is more easily converted by yeast 

 into carbonic acid and alcohol than is either triticin or sinistrin. 



§ 199. Alcolwlates of the foregoing Carhohydrateii, Composition, 

 Quantitative Estimation, etc. — The precipitates of levulin, triticin 

 and sinistrin produced by spirit retain notable quantities of 

 alcohol in such a manner as to necessitate the inference that 

 distinct alcoholates have been formed. Even after standing for 

 three months over sulphuric acid the levulin compound had not 

 lost all its alcohol, whilst in a partial vacuum it had disappeared 

 in the course of two months. Prolonged heating to 110,° a 

 temperature at which the alcoholate melts, is sufficient to cause 

 the gradual expulsion of the alcohol. 



In estimating the four carbohydrates in question by calculation 

 from the amount of sugar yielded by the action of dilute acids, it 

 must be remembered that the composition of dextrin, sinistrin 

 and levulin, dried at 100°, has been found by analysis to corres- 

 pond to the formula C^-H^^Or,, but that triticin dried at 110° 

 has the same composition as cane-sugar : viz., C^^HooO^^. 



In these cases the glucose (§ 76) is better estimated by Fehling's 

 solution (§ 8.3) than by polarization (§ 208). Solutions of levulin, 

 triticin and sinistrin, although inverted Avith dilute acids only, do 

 not always show an angle of rotation = 106° to 107° (§ 205), even 

 if the solution be neutralized, evaporated to dryness, redissolved 

 in cold water, and tested immediately. On cooling the solution 

 after inversion and examining at once, levulin jdelded, in the 

 most favourable instances, a sugar with a rotatory power of 81°, 

 triticin, 94°, and sinistrin, 96° ; and it was only by conducting 

 the inversion in sealed tubes that Reidemeister obtained for 

 triticin-sugar a rotation of 106 '5°, indicating the pi-esence of 

 pure levulose.2 



1 For mycodextrin and myciiiulin see Ludwig and Busse, Archiv d. Pharm, 

 clxxxix. 24, 1869. 



- Compare Keidemeister, loc. cit. . 



