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On the Amount of Phosphoric Acid in the Sea-Water 
off Plymouth Sound. 
By 
Donald J. Matthews. 
In spite of its biological importance, only a few investigators have turned 
their attention to the content of the sea in phosphoric acid. The older 
analyses by C. Schmidt (1) and Forchammer are quoted by K. Brandt (2). 
Schmidt found from 2:8 mg. to 5-5 mg. of P,O; per 1000 grms. of water 
in the colder seas, and from 0-76 mg. to 1-8 mg. in warmer regions, while 
Forchammer found from 4:6 mg. to 12-5 mg. in the Gulf of Finland. 
Kriimmel (4) refers to these as inaccurate, and quotes the results of 
analyses made much more recently by E. Raben, in connection with the 
International Fishery Investigations, as alone reliable. K. Brandt (3) 
also refers to Raben’s work in various papers, but neither the present 
writer nor Professor Martin Knudsen, of Copenhagen, who has very 
kindly made a search also, has been able to find any original paper by 
Raben on the subject, so that we unfortunately know nothing of his 
methods beyond the fact, given by Brandt, that the samples were filtered 
immediately after collection through Schleicher and Schull’s hardened 
paper. This is a very necessary precaution, as there would be danger of 
an increase in the phosphates owing to the decomposition of suspended 
organic matter by bacteria. The present writer has found that even a 
filtered sample cannot be put aside in safety for any length of time unless 
previously sterilised, as the whole of the phosphoric acid may be removed 
by the growth of moulds. 
Kriimmel mentions also some analyses by Sir John Murray as equally 
defective. 
Raben’s samples were collected in the Baltic and North Sea ; he found 
as a rule less than one milligram of P,O; per litre, with a minimum of 
0-14 mg. to 0-25 mg. in February and May, and a maximum of 1-46 mg. 
in the autumn. 
The present writer, in sea-water taken half a mile outside the Break- 
water at Plymouth; has found as a maximum 0-1 mg. per litre, less than 
the lowest result given by any of the workers mentioned above. 
