Chemical and Physical Papers. 



39 



nese dioxide. If the solution is colored brown, add enough am- 

 monium ferrous sulphate to clear the solution, and boil off any 

 oxides of nitrogen. Add a drop of silver nitrate to remove from 

 the solution the last trace of chlorides. Cool to about 16° and add 

 an excess of sodium bismuthate, shake for a few minutes, and filter 

 through a washed asbestos mat free from organic matter. Wash 

 the filter with three-par-cent nitric acid solution, then transfer to a 

 large Nessler tube and make up to 100 cc. Run into another 100- 

 cc, tube, containing sulphuric acid solution made very slightly pink 

 with permanganate, enough standard potassium permanganate so- 

 lution to match the color of the sample. 



Table II. 



The results of the examination of twenty-nine different ground 

 waters from Kansas and western Missouri show the presence of 

 manganese in twelve cases, and a sufficient amount in a few cases 

 to make the water undesirable for a city supply on account of the 

 tendency for " Crenothrix* aiianganfera^' to grow, if for no other 



4. Jr. Soc. Chem. Ind., 21-681: Trans. Amer. Nicro. Soc, 23-32; Hot. Zeit. 1888, bd. 46. 



