14 BULLETIN 983, U. S. DEPARTMENT OF AGRICULTURE. 
value. The work of Korner 28 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 presenct may facilitate the production of 
secondary compounds. 
By prolonged treatment of spruce with concentrated nitric acid, 
Lindsey and Tollens 84 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.fiir ang.Chemie, 1908, 2353. 
» Ibid., 1905, 44. 
30 J. J. D'Orlowski, French Patent No. 405187; also L. Spassky, French Patent No. 45126S. 
a G. Ekstrom, United States Patents Nos. 1087743 and 10S7744. 
82 United States Patent No. 745676. 
m See also Charles Doree and M. Cunningham, " The action of ozone on cellulose III action on beech wood 
(Lignocellulose)"; Jour. Chem. Soc. 103, 677-686; Jour. Chera. Soc. 101, 497-512. 
84 Liebig's Annalen, vol. 267. 341. 
