44 



Papers from the Department of Marine Biology. 



narrow neck, filled, and quickly sealed by applying the blast lamp to 

 the center of this constriction, the part removed being saved for use 

 with sea-water. The blast lamp and all other flames were in a separate 

 room from the burettes. The seal left a point on the tube liable to be 

 broken, but this was covered with a layer of melted chewing-gum 

 followed by a cap of sealing-wax. In the following list of mixtures the 

 first column gives the percentage of the acid solution having 0.3 m 

 boric acid and 2.25 per cent NaCl, the second column the percentage 

 of the alkaline solution of 0.075 m borax and 1.9 per cent NaCl, the 



third column gives the Ph, the fourth column the Ph of sea- water of 

 S = 31.25 grams per kilo (CI = 17.3 per kilo or 17.7 per liter) of the same 

 color, and the fifth column the Ph of sea-water of S = 37.76 (CI = 20.9 

 per kilo or 21.5 per liter) of the same color, the actual volume of acid 

 solution used for a tube in the sixth column and of alkaline solution in 

 the seventh column. Unless otherwise specified, the tubes are labeled 

 according to the fourth column, and those of Ph 7.4 to 7.7 sterilized. 

 The first difficulty encountered was in obtaining a boric-acid solution 

 with the same salt effect on the indicators as the borax solution. 

 Starting from the conclusions of Palitzsch as to the salt value of boric 

 acid, we finally developed the solution given. We have calibrated 

 these tubes with sea-water about 50 times and in all parts of their 

 range. Our tubes are labeled according to column 4 of the table, and 

 include a set of o-cresolsulfophthalein tubes from Pn 7.45 to 8.30 and a 

 set of thymolsulfophthalein tubes from Ph 7.9 to 9.05. The tubes 

 deposit borax crystals when kept long at a low temperature and these 

 crystals should be dissolved by warming the tubes before using them. 



