Hitter Pit in Ajiph's. :yS 



■whereas slices Hoiitiiig on copper sulphate exposed to air were 

 browned right tlirough in this time. On adniitting air the eohiur- 

 less slices rapidly browned on the surface, and more slowly in the 

 deeper water-logged pulp. 



Slices immersed in absolute alcohol slowly browned, especially 

 along the veins, while slices in absolute alcohol under kerosene and 

 in kerosene remained almost entirely colourless after one week, then 

 slowly browning to some extent on exposure to air. In alcohol a 

 little of the tannic acid slowly dissolves out. 



T/ie oxidase ferment . 



The rapidly filtered sap from apples has no j)ower of decomposing 

 hydrogen peroxide, or of turning guiacum l)lue. The pounded pulp 

 produces a slow evolution of oxygen gas, and turns guiacum blue, 

 but the same is shown after the pulp has been soaked in 1 per cent, 

 solutions of mercuric chloride or copp ;r sulphate, and then well 

 washed. Boiled pulp causes a feeble decomposition of hydrogen 

 peroxide, such as is produced by various organic materials or finely 

 divided particles. 



Pulp cells killed by immersal in 1 per cent and (» — 1 per cent, 

 solutions of soluble mercury oi- copper salts turn brown almost as 

 readily as when killed by crushing. The same is shown when the 

 pulp cells are killed by water saturated with chloroform or with 

 chloroform vapour. In one experiment tlie presence of chloroform 

 appeared to retard browning Thus a band of skin 2 centimetres 

 broad was removed around the equatorial peripheiies of two apples, 

 and one was immersed in (a) a 1 per lUOO solution of copper sul- 

 phate, the other in (b) a similar solution saturated with chloro- 

 form. In 1 week the brown tissue was 5 — 6 mm. deep in (b), and 

 8 — 9 mm. deep in (a). Tlie central pulp, however, contained much 

 air in (a), but was nearly fully water-logged in (b), apparently as 

 the result of the influence of the chloroform on the surface tension 

 of the air in the intercellular spaces. The different depths of brown- 

 ing were not therefore due to chloroform retarding the browning, 

 but to aeration acceleratting it. On exposure to air the central pulp 

 of (b) browned inwards rapidly, but that of (a) more slowly. 



If hydrogen peroxide is present tannic acid instead of turning 

 brown with sodium hydrate, gives a light blue rapidly darkening, 

 becoming dirty, and finally brown on standing. Since the pulp 

 cells do not show this intermediate change, but turn directly brown 

 with sodium hydrate, no hydroxyl appears U) be present or to take- 

 part in the oxidation. 



