208 W. C. ALLEE. 



II. Methods. 



The water collections for oxygen samples were usually made 

 according to the method given in Standard Methods for Water 

 Analysis. 1 Where this method was impracticable, as in surface 

 collections, the sample was taken by means of a two-valve 

 rubber bulb. In all cases more than four times the amount of 

 water necessary to fill the sample bottle was run through it 

 before the sample was taken. 



The oxygen determinations were by the Winkler method. 

 The chemicals were added and the titrations were made in 

 the field. 



Salinity was ascertained by the specific gravity method with 

 standardized bulbs loaned by Dr. Mitchell of the U. S. F. C. 

 The salinity is expressed in the tables as calculated from the 

 specific gravity according to the data given by True (19 15). 



The pH was determined colorimetrically by comparison on the 

 spot with standard colors in tubes specially prepared for salt 

 water by Hynson Westcott and Co. Two indicators were used 

 mainly: Thymolsulphonephthalein (thymol blue) with a color 

 range from 8.0 to 9.6 and dibromthymolsulphonephthalein 

 (bromthymol blue) ranging from 6.0 to 8.0. These sets of 

 standard colors were made up in June before they were used in 

 August. 2 Doubtful determinations in the 7.7-8.0 range were 

 tried with both indicators and on occasion with phenolsulphone- 

 phthalein, range 6.6-8.6. This last set of standard colors were 

 made up in distilled water. Such readings were corrected for 

 sea water by subtracting 0.1 from the observed reading. 3 Com- 

 parative readings with this correction applied are given in 

 Table I. 



The water for pH determinations was collected in a new 40 c.c. 

 injecting syringe with a tight-fitting piston, either directly from 

 the surface or from the large container of the standard apparatus 

 used in collecting oxygen samples. This water was also used in 



1 Report of the Committee on standard methods of water analysis. Jour. Inf. 

 Diseases, Suppl. No. i, pp. 1-141. 



2 The dibromthymolsulphonephthalein set was loaned me by Dr. E. B. Powers 

 in 1920 and by Miss Myra Sampson in 192 1. 



3 Atkins ('22) reports the salt error to be almost double that found here. 



