Acidity of Marine Algae 



Lois Clark, 

 University of Washington, Seattle. 



During the summer of 1916 experiments were undertaken at the 

 Puget Sound Marine Station to determine whether the juices of marine 

 algae are acid or alkaline, and what relation if any these reactions bear 

 to rapidity of growth and to the part of plant selected. Three green, 

 eight brown and fifteen red algae were experimented with. All of these 

 gave an acid reaction. 



The morning, noon and evening tests (table 1 ) were made either on 

 the same day or early the next morning between 3:00 A. M. and 6:00 A. M. 

 The material was washed very carefully in neutralized sea-water. The 

 surplus water was then shaken out. No attempt was made to dry the 

 plants entirely. The alga was then put through a meat chopper, in which 

 a medium knife was used. At first the juice was pressed out through a 

 cloth; but this proved unsatisfactory, as very little juice could be forced 

 from the pulp. The results given below were obtained from juice ex- 

 pressed by means of a jelly-press. The chopped alga was placed in a 

 cloth, then put into the press, and pressure applied. 



There was great difficulty in getting a clear solution. Since titration 

 presupposes a clear solution there is a wider limit of error in the results 

 than there would otherwise be. This is especially true for many of the 

 reds, and for two of the greens. To overcome this a charcoal filter was 

 tried, but with little success. 5-10 cc. of the juice with 4 times as much 

 neutralized sea-water was used in each trial. Titration was made with 

 .02 normal sodium hydrate except in two extreme cases. Phenolphthalein 

 and alizarine paper were used as indicators. The latter was fine filter 

 paper dipped in an alcoholic solution of alizarine. The results are stated 

 in per cents of any normal acid. 



From table 1 one is led to conclude that color is not a factor affecting 

 the acidity to any considerable extent ; and that depth of water has no 

 particular influence. From table 2 it appears that the stipe and bulb are 

 more acid during the daytime. Why these should be so and the fronds 

 otherwise, is not clear, for the growing regions are the stipe and fronds. 

 From table 3 it is evident that the receptacles are much less acid than 

 the other parts. But they contain more water, and therefore would con- 

 tain less acid per cc. of sap. The vegetative portions of Fucus (table 3) 



(235) 



