Fixed carbon dioxide was deterroned according to the recommendations in 

 Standard Methods, and the results are recorded as methyl orange alkalinity in 

 terms of calcium carbonate. Pfydrogen ion concentration was deterinLned, in 

 terras of pH units, by the use of La Motte color standards and block comparator. 



All four forms of nitrogen were determined by the methods given in Standard 

 Methods. It should be pointed out here that analysis for nitrogen as albuminoid 

 anmonia does not yield all of the nitrogen in organic form, but only that of the 

 relatively unstable compounds which are readily acted upon by alkaline potas- 

 sium permanganate. Total organic nitrogen cannot be calculated from the albu- 

 minoid nitrogen because the stable and unstable coipounds are not always pre- 

 sent ih the same relative proportions. The figures given by Leighton (1907, 

 Table 63) on the water of the Chicago drainage canal and Illinois River indi- 

 cate that albuminoid nitrogen was, on the average, one half of the total organic 

 nitrogen. It is not improbable that a similar relation exists in the water of 

 Lake Erie. 



Data and Discussion 

 Island Section 

 Oxygen, carbon dioxide, and hydrogen-ion concentration 

 Season of 1928 



Investigation of the chemistry of the water in 1928 was carried on in 

 connection with the study of larval fish. Samples were taken at a large 

 number of stations but they were not visited frequently enough to show the 

 seasonal changes completely. Moreover, most of the determinations were made 

 on the deck of the Investigator , often under the most unfavorable conditions 

 for such work. The coloro:netric determination of small amounts of free car- 

 bon dioxide is difficult in the laboratory, and it would be surprising if 

 accurate results were obtained on the deck of a small boat, -some of the data 

 on free carbon dioxide given in Table 25 appear to be erroneous since they show 

 no rrlationship to the dissolved oxygen and pH, which, in most cases, are in 

 close agreement. 



Only a small part of the data will be presented here. The data from 

 Stations 13, 59A, and 76 are given in Table lU. The location of Stations 18 

 and 59A may be seen in Fig. 1. Station 76 is located a short distance south 

 of Green Island, which is off the west shore of South Bass Island. Tempera- 

 tures were taken with a Fahrenheit thermometer which was read to the nearest 

 degree. These figures were changed to the centigrade scale, and recorded in 

 degrees and half degrees to avoid fictitious accuracy. 



The data will be discussed briefly as a group. Dissolved oxygen in the 

 rurface stratum was high for all samples. In four instances there was super- 

 saturation, and the per cent of saturation never fell below 86. Most of the 

 ^ottom samples showed some reduction in oxygen, but in no case did it fall 

 below 62 per cent, so that the depletion was never serious. 



61 



