RY R. GnEIG-SMITH. 611 



The optical activity of tlie products of hydrolysis was deter- 

 mined V)y preparing a fresh extract of soil (400 gr.) in the manner 

 already described, and boiling all the substances brought into 

 solution, with 5% sulphuric acid. After treatment with barium 

 carbonate, basic lead acetate, sulphuric acid, and animal charcoal, 

 a comparatively colourless solution measuring 100 c.c. was 

 obtained. This gave the following: — 



Volatile mid organic matter 1 '67 g. 



Copper reduced 2'44.3g. 



Equivalent to dextrose or galactose 126 g. 



Rotation in 2 decim. tube +0'99° 



From the copper equivalent and the rotation, the specific rota- 

 tion of the mixture appears to be [a]D= -t-39"3°, which is so much 

 below the specific- rotation of a mixture of dextrose and galactose, 

 that we must infer that the unknown sugar is Ifevorotatory. An 

 examination of the rotation at different temperatures was kindly 

 made by Mr. Thos. Steel, who informed me that no levulose was 

 present. 



It is advisable to prolong the heating in the autoclave, to get 

 as much gum as possible into solution. In a preliminary experi- 

 ment, the heating was given at quarter-hourly intervals, and each 

 heating brought gum and its hydrolytic products into solution. 

 In another preliminary experiment, an ordinary agricultural soil 

 was used, but no hydrolysable gum was obtained by heating for 

 one-quarter of an hour. The alcohol-soluble portion was not 

 examined. Possibly the smaller (juantity of gum had been 

 hydrolysed. 



The prohmged four hours' treatment in the autoclave made the 

 soil distinctly acid. l^'ifty c.c. of a 50% extract of soil showed a 

 faint colour to phenolphthalein with 3-75 c.c. of tenth-normal 

 alkali, a deep coloui- being obtained with 5-7 c.c. It was neutral 

 to litmus paper with 3-7 c.c. This suggested that possibly the 

 toxic effect produced upon heating soils may be due to a forma- 

 tion of acid, but upon testing a few soils that had been heated 

 for four hours at 105°C., no excess of acid could be detected by 

 stirring up the soil to a paste with water to which varying 

 amounts of F/IO alkali had been added. 



