m ] SCH REINER &• REED-OXIDIZING POWER OF ROOTS 3° 



aloin, and leuco-rosolic acid. Alcoholic solutions of guaiac were 

 also used for various tests, but could not be put into solution cultures 



containing growing roots. 



The value of phenolphthalin, a leuco-compound prepared Irom 

 phenolphthalein, as an indicator of oxidizing enzymes, has been 

 demonstrated for plant work by Kastle" and by Raciborski 



rnenoipntnaim is preptueu uy mv u^**^ . ■ 



which consists in reducing ordinary phenolphthalein with zinc dust 

 and sodium hydroxid to phenolphthalin. The latter substance 

 is oxidized back to phenolphthalein by the oxidizing power ot the 

 plant roots, a change which is readily demonstrated when the solu^ 

 tion is rendered alkaline. The following procedure was observed 

 in preparing this reagent. Weigh out 250- of phenolphthalein, 



3 gm of sodium hvdroxid, and 4 or S gm ° f zinc dust PlaCe ^ "\ 

 flask and add 100 to 1 so" of water. Place the flask on a sand bah 

 and heat sufficiently to cause a rapid evolution of hydrogen, without 

 causing the contents of the flask to boil violently. to**»*T£ 

 requires 2 to 3 hours to effect reduction of the j*^*T^ 

 The contents of the flask, after reduction is completed, may be hltere 

 and rendered nearly neutral with hydrochloric acid, and may then 

 used as an indicator in the plant cultures. However, better result 

 may be obtained by using phenolphthalin purified accordm to the 

 method given bv Baeyek. After purification the £"*£££ 

 is dissolved in N/10 or N/20 NaOH and a few cubic — 

 of the alkaline solution put into each culture, adding eq-U— 

 to cultures which are to be compared. If quantitative 

 fcired, it is necessary to reduce aU the solution cultures to neurit, 

 or the same degree of alkalinity. A very shght *#•«•' 



« not usually Sd to plants within **£~£Z3£Z b 

 «1 is favorable to the process of oxidation. Phenoip ^^ 

 *>wly oxidized by mere contact with the air; theretore ^ ^ 



to instal controls which will allow the results to be ^ ^ 



atmospheric oxidation. When the phenolphthalin ^ 



*tion cultures, a like quantity is therefore added* ja^ ^ ^ 



' Amer. Chem. Jour. 26:526. 1901. Hyg. Lab. U. 



' »ujci . v^iieiu. juui 



H °sp. Ser. Bull. 26. 1906. 



23 Bull. Acad. Sci. Cracovie, Math. Nat. CI. IQ05'33»- 



34 Annalen Chem. 202:80. 1880. 



