14 BULLETIN 983, U. S. DEPARTMENT OF AGRICULTURE. 



value. The work of Korner 2S and of Reiferscheidt 29 also substan- 

 tiates in the main that of Simonsen. Korner attempted to duplicate 

 Classen's work with sulphur dioxide, but could not. Reiferscheidt 

 obtained Classen's yields by using a longer cooking period than that 

 specified by Classen. In addition, several other investigations have 

 been made in which hydrofluoric 30 and other similar acids were 

 used. These investigations are of scientific rather than technical 

 interest, and reference to them may be found in the bibliography. 



Different from the processes mentioned above, in which the inver- 

 sion of the wood is brought about only by heating with mineral acids, 

 is that class of processes in which the cellulose or wood substance is 

 changed to oxycellulose, acid cellulose, cellose, 31 soluble cellulose, or 

 hydrocellulose before the real inversion takes place. Mention has 

 already been made of Girard's work and Neumann's adaptation 

 thereof. Gentzen and Roth 32 patented the use of ozone 33 as an 

 oxidizing agent in conjunction with sulphuric acid. A yield of 34 

 per cent of dextrose is claimed in the patent, but Korner, in repeating 

 the work, could not obtain any increase in yield over that obtained by 

 sulphuric acid alone. 



Korner further investigated the effects of hydrogen peroxide, potas- 

 sium dichromate, and potassium persulphate in conjunction with 

 sulphuric acid. Hydrogen peroxide increased the yields about 50 per 

 cent above those obtained^ with sulphuric acid alone, whereas potas- 

 sium dichromate, potassium persulphate, and ozone all decrease the 

 yields. The use of salts, such as the dichromate and persulphate, may 

 be criticized in that their presence may facilitate the production of 

 secondary compounds. 



By prolonged treatment of spruce with concentrated nitric acid, 

 Lindsey and Tollens 34 prepared an oxycellulose which could not be 

 hydrolyzed to a sugar under any condition. If we consider that the 

 salts present in Kroner's experiments exerted no deleterious action 

 and were inert during the inversion, then the results of Lindsey and 

 Tollens seem to be in accord with those of Kroner, in that the oxycel- 

 lulose prepared by them was the final product of oxidation, and the 

 product obtained by Kroner with potassium dichromate or persul- 

 phate was an intermediate product, some of which could be hydro- 

 lyzed. Perhaps only a part of the wood was completely oxidized, and 

 the yields of sugar obtained were on the remaining material which 

 had not been acted upon by the oxidizing agent. 



28 Zeit.fur ang.Chemie, 1908, 2353. 



2 9 Ibid., 1905, 44. 



8 ° J. J. D'OrlowsM, French Patent No. 405187; also L. Spassky, French Patent No. 451268. 

 81 G. Ekstrom, United States Patents Nos. 1087743 and 10S7744. 

 83 United States Patent No. 745676. 



88 See also Charles Doree and M. Cunningham, " The action of ozone on cellulose III action on beech wood 

 (Lignocellulose)"; Jour. Chem. Soc. 103, 677-6S6; Jour. Chem. Soc. 101, 497-512. 

 M Liebig's Annalen, vol. 267, 341. 



