CAS EXPERIMENT STATION RECORD. 



materials with 1.25 per cent salpliuric acid and determined the portion 

 wliieli had been dissolved and the resulting sugar (probably with Feh- 

 lina's solution), lie heated the residue from this digestion with 1.25 per 

 cent potassium hydroxid and likewise determined the portion dissolved 

 (no sugar could be recognized in this solution). The results are given 

 in the following table : 



AinoHiilfi (lisi^olrcd hi/ diliile mid and alkali, mid siicjar in ike n-siiUini/ solutions. 



Rye. 



Meadow 

 bay. 



Per cent, i Per cent. 



Crimson 

 clover. 



Per cent. 



Dissolved by 1 .'lo per cent sulphuric acid 48. 12 I 28. 39 j 19. 44 



Dissolved by 1.25 per cent potassium b\ droxid I 34. 57 | 24. 65 | 31. 84 



Total dissolved j 82.69 1 53.04 1 51.28 



Sugar resulting from digestion with : I 



1.25per cent sulphuric acid.-- 19.21 8.33 1.84 



1.25 per cent potassium lij'droxid a None. None. I Xone. 



alt is not .surprising that no sugar could be found in the 34.57 per cent of material dissolved by the 

 1.25 jjer cent jiotassium hj-droxid, since ■weak potash solution does not invert "condensed"' carbohy- 

 drates, and for the most part so changes any hexoses present or formed that Ihey do not react 

 upon Fehling's solution at all or only weakly. 



Hence only a small i)roportion of the substance dissolved from the 

 above materials by 1.25 per cent of suli>huric acid was recov.'red in the 

 form of sugar. Even allowing that the dissolved portion of '' condensed'' 

 carbohydrates was only incompletely hydrolyzed to hexoses by the 

 weak sulphuric acid, the difference between the 48.12 per cent of sub- 

 stance dissidved from rye, for instance, and the 19.21 per cent of sugar 

 found in the solution is very large. 



These observations give rise to great uncertainty, but show conclu- 

 sively that the percentages of nitrogen -free extract found by the Weende 

 method represent not only the soluble carbohydrates of feeding stuflts, 

 but many other substances as well. 



OTHEll UNCERTAINTIES AS TO THE FKtURES FOR NITROGEN-FREE 



EXTRACT. 



Since the nitrogen-free extract is determined by difference, it is evi- 

 dent that all the errors in the determination of the other constituents 

 are accumulated in the nitrogen-free extract. Of the substances deter- 

 mined directly, the ash is in general the least open to objection. Little 

 objection can be made either to the determination of fat or crude fat, 

 although the material extracted with ether is at times of quite a mixed 

 nature.^ 



More objection can be made to the protein calculated from tbe nitro- 

 gen by the factor G.25, which assumes that the protein substances con- 

 tain 10 per cent of nitrogen. While this assumption holds good in 

 case of some proteids, it does not in case of others. The proteids of 



•Regarding the nature of the crude fat, see, among others, E. Schulze, Laudw. 

 Vers. Stat., 15 (1872), p. 81; Konig, Landw. Vers. Stat., 13 (1870), p. 241. 



