Catalysts of Organic and Inorganic Origin. 



287 



Poison. 



Colour change 

 in air. 



Gruaiaeum test. 



TV 



.Decomposition 

 of HoO.,. 



Untreated 







Brown 



Blue 



Active. 



■ 1 per cent 



HgCl 2 





None 



Pale blue 



1 eebie. 



1 



CuS0 4 





>> 



Deep blue 



Strong. 



1 » 



Pb.,N0 3 





J? 



Pale greenish or 



No blue 



None. 



5 „ 



Pb 2 Ac 





Pale blue 



Fairly active. 









yellowish brown 







1 .. 



AgNO-j 





Blackens 



Strong blue especially 



None. 









with H 2 2 





1 



morphine sulphate 



Brown 



Pale blue 



j? eeuie. 



10 „ 







» 



jj 



)) 



10 „ 



brucin nitrate 





>> 





>) 



2 



BaCIO, 





None 



Deep blue 



)) 



2 „ 



FeCl, 





Rapidly changing 



Active. 









to dark brown 











None 



Faint blue 



Doubtful. 







Nil 



Nil 



Very feeble. 



With fresh juice or pulp from potatoes the following results were 

 obtained : — 



Poison. 



Colour change 

 in air. 



G-uaiacum test. 



Decomposition 

 of H 2 0o. 



5 per cent, lead nitrate 



5 „ mercuric chloride 

 5 copper sulphate ... 



Untreated 



Boiled 



Nil 



>> 



Brown 

 Nil 



Nil 

 Blue 

 Deep blue 

 Strong blue 

 Nil 



Nil. 



Very feeble. 



Active. 



Active. 

 Very feeble. 



At first sight these results seem to show that browning is not closely 

 related with the presence of the oxidase. With absolute alcohol, however, if 

 the pulp is allowed to stand for a short time the oxidase reactions entirely 

 disappear. Apparently the alcohol first weakens and then destroys the 

 oxidase and the oxidation of tannic acid seems to require a more powerful 

 oxidase action than is necessary to produce a blue with guaiacum. 



Inorganic Oxidases. 



In addition the influence of the metallic poisons must be taken into 

 account. According to L. Meyer,* salts of manganese such as the chloride 

 and sulphate can act as strong oxidases, and salts of copper, iron, and cobalt 

 have the same power but progressively decreasing, whilst the least oxidase 

 action is shown by salts of nickel, zinc, cadmium, and magnesium. It is not, 

 however, clear as to whether a strong metallic oxidase oxidises all substances 



* ' Ber. Chem. Gesell.,' vol. 20, p. 3085 (1887). 



