178 III. CHEMISTRY OF NEUTRAL FATS 



settled. Although the earlier results of Thomas and WeitzeF^-'^* indicated 

 the toxicity of the iso-acids as demonstrated by rat growth tests, later re- 

 sults^^ indicate that the fats from the Fischer-Tropsch process are almost 

 completely utilized, in spite of the fact that they must have contained an 

 iso-acid contend® of 35%. In tests on man, Thomas''^ found an average 

 loss of 3-4 grams of iso-acid in the urine after consumption of synthetic 

 fats in amounts of 100-220 g., although in one case the value rose to 9 g. 

 Thomas believes that only those fatty acids containing more than one 

 branched chain fail to be metabolized. On the other hand, it is claimed" 

 that the Witten fat can be purified by a process involving extraction with 

 methyl formate and related solvents so that a product is produced which 

 has no inhibitory effect on groA\iih.'''' This is believed to be safe for con- 

 sumption by human subjects. More information is needed before the 

 problem of toxicity can be definitely settled. This is especially the case in 

 view of the possible unreliability of some of the data obtained during the 

 war. Since the Nazis considered the production of sjTithetic fats as a 

 triumph for German science, unfavorable reports were withheld or sup- 

 pressed. Moreover, the authors who reported favorable results tended in 

 some instances to be overenthusiastic in their commendation of the syn- 

 thetic fats. 



In the Witten plant, 40,000 tons of "gatsch" were processed per year 

 into 31,000 tons of fatty acids. Only 5% of the latter, or 1550 tons, were 

 available for the production of edible fats. The claim that the cost of 

 synthetic fat was decreased to that of natural fat during 1943-1944 was 

 based upon the assumption that the by-product, "gatsch," costs nothing. 

 On the basis of assigning a fair charge for this source material, Vincent*^ 

 has estimated the cost as $708 per ton in Germany (35.4 cents per pound), 

 and $821 per ton in England (41.1 cents per pound). In addition to the 

 review of Thomas and Weitzel,^* the reader is referred to the monograph of 

 Wittka.'s 



" K. Thomas and G. Weitzel, Deut. med. Wochschr., 71, 18-21 (1946); Chem. AhsL, 

 41, 1342 (1947). 



"K. Thomas and G, Weitzel, Z. physiol. Chem., 282, 180-185 (1947); Siiddeut. 

 Apoth.-Ztg., 87, 255-256 (1947); Chem. AhsL, JfS, 5097 (1949). 



^^ K. Thomas, Unpublished results cited in F. A. O. Report, Synthetic Fats, Washing- 

 ton, D. C., Nov. 3, 1948, p. 4. 



76 H. Kraut, A. Weischer, and R. Hugel, Biochem. Z., 316, 96-107 (1943); 317, 187- 

 192 (1944). 



" H. Appel, H. Bohm, W. Keil, and G. Schiller, Z. -physiol. Chem., 274, 186-205 

 (1942). 



7* F. Wittka, Moderne Fettchemische Technologie. 11. Gewinnung der hoheren Fettsau- 

 ren durch Oxydation der KWSe, Barth, Leipzig, 1940; Chem. Abst., 39, 2000 (1945); 

 Seifensieder-Ztg., 66, 666-668, 669-700 (1939); Chem. Abst., S3, 9603 (1939); Allgem. 

 Oel-u. Fett-Ztg., 38, 358-360, 397-399 (1941) ; Chem. Abst., 37, 2201, 3959 (1943). Cited 

 by K. Thomas and G. Weitzel, in R. Kuhii, Fiat Rev. German Set., Biochemistry, 1, 35 

 (1947). 



