412 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



(3) a-naphthol. A I per cent, solution in equal parts of water and 

 alcohol. When oxidised it becomes lavender in colour. This sub- 

 strate has been largely used in botanical work. 



(4) Guaiacol. A 2 per cent, solution in alcohol. It is oxidised to 

 tetraguaiacoquinone, which is red 



(5) Benzidine. A I per cent, solution in 50 per cent alcohol. It 

 becomes blue on oxidation and a brown precipitate is formed. 



(6) /-phenylenediamine hydrochloride. A I per cent solution in 

 water. It becomes greenish in colour. 



(7) Indophenol. A I per cent a-naphthol solution in 50 per cent 

 alcohol and a I percent aqueous solution of/-phenylenediamine hydro- 

 chloride are required. 2 or 3 drops of each of these are added to the 

 enzyme solution which is made faintly alkaline with sodium carbonate. 

 A purple solution results. 



A few drops of any of these reagents are added to about 5 c.c. of 

 the oxidase solution to which a few c.c. of hydrogen peroxide have 

 been added. The colour slowly forms. 



Peroxidases are present in milk and blood (pp. 458, 476). 



The direct oxidase may be observed in potato : a drop of guaiacum 

 solution is placed upon the cut surface ; in a short time it becomes 

 blue. 



The presence of an oxidase in minced tissues is readily detected by 

 the indophenol reaction as shown by Vernon. 1 The reaction takes 

 place according to the equation : 



C,H 4 (NH 2 ) a + C 10 H 7 OH + O a = C 6 H< + 2 H 2 O 



\N C 10 H 6 

 p-phenylene- a-naphthol. 

 diamine. 



The substrate consists of "144 per cent solution of a-naphthol 

 (01 M) and *n percent paraphenylenediamine('OiM) in 50 per cent 

 alcohol. 5 cc. of the solution together with about 5 c.c. of -I per 

 -cant sodium carbonate solution are poured upon *5 to I gm. of minced 

 tissue in a flat dish (a Petri dish 8 -8 cm.) and well stirred with the 

 tissue. The indophenol begins to form almost at once. 



1 J. Physiol., 42, 402. 



