120 Lily Bell Sefton 



phates; and the analysis was conducted according to a scheme 

 given by Leffman,^ although it was found necessary to make 

 several modifications of his plan. 



Before the actual analysis began, all the reagents and solu- 

 tions to be used were very carefulh" prepared and standardized. 

 Just here it may be well to mention one thing, which was learned 

 by hard experience, and without which it will be impossible to 

 secure results in any way satisfactory. It is this : use absolutely 

 ammonium-free (and this, usually, will be also nitrite-free) water 

 in the preparation of all reagents. To secure such water, twenty 

 grams of potassium h3^droxide and five-tenths grams of potas- 

 sium permanganate were dissolved in a liter of ordinar}^ distilled 

 water, and then the solution was re-distilled by means of a Kjeldahl 

 apparatus. The water obtained was used in making up another 

 and stronger solution of the same kind. Two hundred grams of 

 potassium hydroxide and eight grams of potassium perman- 

 ganate were dissolved in a liter of this water, and fifty cubic 

 centimeters of this solution were added to every liter distilled 

 afterward. Water will remain ammonium-free for only a com- 

 paratively short time, so the reagents must be made up imme- 

 diately. 



The water to be tested was collected in two-liter bottles, made 

 of green glass and provided with tightly-fitting stoppers. Since 

 the purpose of this analysis was to establish a standard of pur- 

 ity, samples were not taken from any wells save those thought 

 to be pure. This was determined by ascertaining that the well 

 was not located near, nor in any way connected with, such sources 

 of impurity as barnyards, cesspools, and vaults ; by making sure 

 that no sickness had ever been traced to the use of the water; and 

 by finding out how recently and why the well had been cleaned. 



Three analyses were carried on at a time. Owing to the varia- 

 bility, from time to time, of the quantities of ammonium, nitrites, 

 nitrates and oxygen-consuming power, these were tested for 

 first, while the tests for chlorine, phosphates, and dissolved 

 solids were left till later. 



In testing for ammonium, standards containing a known equiv- 

 alent of ammonia were nesslerized and then the first three or 

 four distillates (similarly nesslerized) were compared with these. 

 After the free ammonia had been driven off, the remainder of 



* Henry Leffinan, Examindlioit of Water for Sanitary and Technic Purposes, 1895. 



