NORTHWESTERN LAKES OF THE UNITED STATES. 
63 
Tillmans and Heublein (1911) determined carbon dioxide by weight, using 
Winkler’s method, and checked it by titration. They conclude that the acid 
carbonates are neutral to phenolphthalein and are not affected by chlorides, nitrates, 
or sulphate of sodium, calcium, or magnesium. 
Winkler (1914a) titrated the free carbon dioxide in potable waters with a 
solution of sodium carbonate, each cc. of which was equal to 1 cc. of carbon dioxide 
per liter when used on a 100 cc. sample. He used phenolphthalein and titrated to 
a pink color that was permanent for five minutes. 
His results show that calcium carbonate does affect the results, and he cor- 
rects the result by adding 0.1 cc. of C0 2 for each 5° of hardness. (One degree of 
hardness of the German scale is equal to 17.9 parts of calcium carbonate per mil- 
lion.) This correction would apply to such lakes as have a fixed carbon dioxide 
content of practically 20 cc. per liter. Each 20 cc. of free carbon dioxide 
should be increased by 0.1 cc. This would apply to Medical and Bear Lakes and 
a few of the hard-water lakes, such as Silver and Clear in eastern Washington. 
In most lakes the correction would be inside the limit of error. 
Winkler also adds sodium potassium tartrate when iron is present and noted 
that manganese had little effect. 
Johnston (1916) reviewed and discussed the whole subject of titrating carbonic 
acid in natural waters. 
COMPLETE ANALYSES OF WATER OF FIVE IMPORTANT LAKES. 
It was originally planned to have a complete analysis made of the water from 
each of the more important lakes, but the trouble and expense involved in getting 
the samples to Washington proved so great that it was abandoned. The five 
analyses given below prove the importance of further work along this line. 
The most interesting analysis in this set is that of Bear Lake. In the first 
place it contains a much larger amount of dissolved solids than any other lake 
containing fish that has been examined in this section. The magnesium content 
of the water is very unusual, it being many times greater than the calcium content. 
The fact that the water contains a fairly large quantity of zinc is also of interest. 
The other analyses are not unusual, but they are published here in hopes that 
others may be published later so that all may be compared. 
