1044 Journal of Agricultural Research vol. vi,n . 25 



The substance was further purified by subliming several times at a low 

 temperature and was dried over anhydrous calcium chlorid. 



The properties of the substance thus obtained were found to be iden- 

 tical with those of a-crotonic acid. The purified soil substance melts at 

 72 ° C, while a-crotonic acid melts at 72 °. A mixture of Kahlbaum's 

 chemically pure a-crotonic acid (further purified by sublimation) and 

 the soil compound melted at 72 . 1 



The purified soil compound is soluble in water, ether, alcohol, and 

 slightly soluble in cold and more soluble in hot petroleum ether. It has 

 a sharp odor somewhat similar to that of butyric acid, although much 

 milder. It readily reduces potassium permanganate in a cold alkaline 

 solution. In a cold aqueous solution it decolorizes bromin instantane- 

 ously, but does not decolorize bromin in carbon tetrachlorid. With 

 ferric chlorid it gives an orange color on the spot plate. In aqueous 

 solution it does not reduce gold chlorid in the cold. 



A determination of the neutralization equivalent (molecular weight) 

 gave the following results: 45.3 mgm. of the soil compound required 

 10.43 c - c - °f N/10 sodium hydroxid (NaOH) for complete neutraliza- 

 tion with phenolphthalein as the indicator. 



The neutralization equivalent was found to be equal to 86.8. 



The neutralization equivalent calculated for crotonic acid (CH 3 CH:- 

 CH.COOH) is 86.05. 



The soil substance sublimes readily at room temperature, which is in 

 accord with the observation made by Bulk (1). 



These reactions and tests on the soil compound and synthetic a-crotonic 

 acid were carried out simultaneously and were found to be identical in 

 every case. The crystalline forms were also found to be the same. Fig- 

 ures 1 and 2 of Plate CXIV show the form and similarity of the crystals 

 obtained in the first stage of sublimation. During the process of sub- 

 limation the crystals grow into large irregular plates or leaflets. 



Ninety-four mgm. of the acid were obtained from 50 pounds of soil. 

 This quantity would correspond approximately to 16 pounds per acre. 

 It is obvious from the very unusual properties of this substance that a 

 considerable amount would be lost in the processes of isolation and 

 purification, and the actual amount present in the soil would be much 

 greater than 16 pounds per acre, which is therefore a minimal value. 



The a- and /3-crotonic acids are unsaturated and have the formula 

 CH 3 CH:CH.COOH. These acids are typical examples of compounds 

 which exhibit geometrical isomerism. Their structures have been dwelt 



1 In all cases a slight softening or sintering at 69 to 70 was observed, which may be due to the presence 

 of traces of 0-crotonic acid. Morrell and Hanson (4, p. 1322) have shown that a-crotonic acid, when heated 

 above its melting point, is partially converted into /S-crotonic acid in amounts varying with the tempera- 

 ture. This study indicated the advisability of subliming a-crotonic acid at a low temperature in purifying 

 it in our work. In order to prevent the loss of material by sublimation, the melting points were made in 

 sealed tubes which were completely submerged. 



