PROPERTIES OF GROWTH SUBSTANCES 47 



from peanut, sunflower, mustard, and linseed oils (Mitt. IX, 

 1934) . Preliminary tests indicated that maize oil is rich in growth 

 substance. Preparation of the auxin was started with 16 kg. 

 maize oU, divided into separate 1 to 2 kg. portions. Each 

 portion was mixed with twice its volume of water and shaken for 

 3 hours, then centrifuged. The aqueous solution was acidified 

 with hydrochloric acid and then extracted with ether. The pro- 

 cedure from this point on is essentially the same as that for 

 obtaining auxin from urine. After auxin a was removed, the more 

 active fractions that boiled at lower temperatures yielded crystals 

 with a melting point of 183°C. (auxin h) in contrast to 196° for 

 auxin a. 



Auxin b has an average physiological effectiveness of 50,000,000 

 AE per milligram. 



Urine, a Source of 3-indole Acetic Acid (Heteroauxin). — Kogl, 

 Haagen Smit, and Erxleben (1934, Mitt. XI) prepared another 

 growth substance from urine which they called heteroauxin. 

 It is 3-indole acetic acid and had been isolated previously 

 (Salkowski, 1885) from normal and pathological urines. It has 

 been prepared synthetically by Majima and Hoshino (1925). 



The total growth-substance content of urine is about 80 per 

 cent auxin a and 20 per cent 3-indole acetic acid (Kogl, Haagen 

 Smit, and Erxleben, 1934, Mitt. XI). The physiological activity 

 of the latter is approximately 25,000,000 AE per milHgram. It 

 was prepared from urine in the following way : 



(1) One kilogram decolorizing carbon was mixed with 100 liters 

 urine and allowed to stand overnight. The charcoal then had 

 settled so that the fluid could be siphoned off. The charcoal 

 was drained and washed with water. (2) Next it was mixed 

 with 2 liters aqueous acetone ammonia (60 per cent acetone, 

 5 per cent ammonia) ; this carbon infusion was filtered off quickly, 

 and a fight yellow eluate remained. (3) Five liters of acetone 

 ammonia (60 per cent acetone, 2.5 per cent concentrated ammonia) 

 were siphoned through (preferably overnight). The entire 

 eluate was stirred thoroughly with an excess of ammonium sul- 

 phate, until the fluid had divided into two layers of about the 

 same depth. The upper auxin- containing layer was siphoned 

 off and distilled. The last remains of the acetone were removed 

 in a vacuum. (4) The residue was dissolved in water and 

 extracted with ether, the ether residue boiled in petroleum ether 



