FIELD TESTS TABLET METHODS 511 



in enough of the strong water to discharge the red color. Then, having 

 found the amount of chlorine in it, a known greater quantity of the water 

 may be added and enough tablets then to bring back the red color. One 

 may thus alternate two or three times. 



Carbonates. — Leighton's test, the addition of sodium acid sulphate 

 with methyl orange or phenol phthalen, as indicators, is as simple as the 

 chlorine test, but not so trustworthy, since it will not work in the presence 

 of calcium chloride, for instance. This gives the acid reaction at once, 

 even though carbonates are really present. 



A solution of soap and soda, pink with phenol-phthalein, is made color- 

 less by enough of the strong calcium chloride waters, and may be as a 

 rough index of the amount of calcium chloride. 



Hardness. — The test for hardness (Ca and Mg) with soap tablets, 

 equivalent to a Icnown amount of CaCOg, is also a practical vest-pocket 

 test. In strong mine waters it has been found well to make up a solution 

 of a number of tablets in a known amount of water, and then add the 

 water from a gradiiated burette until the foam is discharged. 



In general. — ]\Iaterial for the above tests can be carried in tlie vest 

 pocket and are those I have most used, especially the chlorine. 



TURBIDITY METHODS 



CMorine. — Other tests have })een devised which involved forming a pre- 

 cipitate and seeing how opaqi;e or turbid it made the water. For in- 

 stance, in our Huron County work,-'' Davis and I graded them as — trace, 

 precipitate witli AgNOg opalescent, less than 100 per million CI present ; 

 low, precipitate with AgNOg milky, 200 to 600 per million CI present; 

 medium, precipitate with AgNOg curdled, 600 to 1,300 per million CI 

 present, with a taste; above this the salty taste was distinct. 



In Leighton's tests a portable electric light and battery are used, which 

 are rather heavy. No doubt other methods more portable, but perhaps 

 less accurate, could be devised which would suffice to compare tlie various 

 waters found in a particular mine. It might be well to have made up 

 tablets containing known amounts of substances to be tested for, which 

 could be iised to make solutions for comparison. 



Calcium. — Leighton did use the turbidity produced by ammonium ox- 

 alate with a little excess of ammonia, but it has been canceled. It seems 

 to work pretty well with our waters. 



Sodium carbonate might be used, allowing for tlie small amount (30 

 parts per million or so) of calcium carbonate that would remain. 



23 Volume vii, Michigan Geological Survey, part 11, pp. 139-141. 



