THE NITROGEN-FKEE EXTRACT OF FEEDING STUFFS. 



647 



coiitaiiiiiig- approximately 55 per cent. In later years Lindsey, Street, 

 and Tollens ' arrived at the same conclusion as to the richness of liguin 

 in carbon from investigations on the lignin substances dissolved from 

 wood manufacture of cellulose for [)a|)er making. In the course of 

 this [»rocess of manufacture the lignin substances are dissolved by the 

 suli)hurous acid or soda, as sulphonic acids, and probably liave the 

 approximate composition CjiiHiOy (Lindsey and Tollens), or 036H4,.O):j 

 (Street and Tollens), with several molecules of water added. 



The fonnulas found by Lindsey, Street, and Tollens call for 63.3 to 

 04.2 ])er cent of carbon and (!..} per cent of hydrogen, and in this respect 

 are in accord witli the composition of lignin as given by Bertrand- which 

 calls for ()[.S per cent of carbon, 5.8 per cent of hydrogen, and 1.5 per 

 cent of nitrogen (according to which lignin is a nitrogenous material). 



Otlier .substances of varioKS Muds. — There are still other substances 

 which are not determined as fat, protein, crude liber, or ash, and conse- 

 quently fall under the head of nitrogen-free extrac^t. These are largely 

 aromatic substances — tannic acid especially — which belong to the color- 

 ing matters, alkaloids, etc., whose nature as well as feeding value is 

 difficult to define. 



MIXED NATITliE OF THK NITROGEN-FREE EXTRACT. 



The material grouped under the name of nitrogen-free extract is 

 accordingly a very complex mixture in which carbohydrates predom- 

 inate, but in which many other substances occur. 



It can be easily proved that nitrogen-free extract contains other sub- 

 stances besides carbohydrates by determining the separate carbohy- 

 drates by ordinary methods. If this is done the total amount of carbo- 

 hydrates may sometimes be approximately equal to the nitrogen-free 

 extract, but there is more apt to be a deliciency. For instance, Wash- 

 burn and Tollens^ obtained the following results with samples of sweet 

 corn in different stages of ripening: 



Total carbohydrates and nitrogen-free extract in sweet corn. 



NitnigeJi-frco extract by Wtjcndc method (by diflerenco) ... 

 Total ciirboliydratcs, detenu iiied directly 



Very 

 young. 



Per cent. 

 57.52 

 37.12 



Similar results were obtained by Atwater.' Less significant but 

 noteworthy results were obtained by Krauch. He digested various 



iLiebi^'a Ann. Cheni., 207 (1892), p. 341 ; Street, luaufj:. Diss. Gottiugen, 1892. 

 - Bui. Soc. Chim. Paris, ser. 2, 7, p. 469. 



^'I.iebiM's Ann. Cliem., 257 (1890), p. 156; .Jour. Liindw., 37 (1889), p. 503. 

 'Amor. .Jour. Sci., 48 (1869), p. 352. 



