1873.] B. Waldie— 0?i tlie Muddy Water of tie JlurjlL 223 



proportion of '07 gramme to 1 litre or 1000 cub. centimetres or 7 pounds to 

 100,000 pounds of water, which is equal to 700 pounds to 10 million pounds 

 of water or to 1 million gallons. From this the quantity of any other of the 

 substances given in the table may be calculated from the last column by 

 simple proportion. Thus as 100 Carbonate of Lime is to 700 pounds 

 required, so is 136 Sulphate of Lime to 952 pounds required, or 2"74i 

 Perchloride of Iron to 19*18 pounds required for 1 million gallons of the 

 muddy water of the Hugli. 



It is necessary to remember, however, that the table given refers to the 

 dry substances, which is the natural condition in which they are usually found 

 in only a few of the substances enumerated in the table, such as Common 

 Salt and Carbonate of Lime. Most of the other substances contain water 

 of cr^^stallization or water of solution, which last may be a very variable 

 quantity. In the latter case the quantity of dry matter in solution must 

 be known. The following table includes a few of the preceding substances 

 most likely to be of practical application : — 



Table of absolute quantities of substances nece^^sary for the clarification 

 of 1 million gallons of muddy loater of the Hugli during the rainy season, 

 calculated from the data given above. 



Pounds. 



Common Salt, dry, equiv. 58-5, 32,760 



Chloride of Calcium or Muriate of Lime, fused or dry, eq. 55 '5,. 1554 



Carbonate of Lime, dry, eq. 50, 700 



Gypsum or native cryst. Sulphate of Lime, eq. 86, 120tfe 



Sulphate of Iron cryst., eq. 139, 159'6 



Alum cryst., eq. 151-2, 55*4 



Perchloride of Iron, dry, 54-7 19*15 



It may be also worth noting the proportion of a few of these sub- 

 stances to the water, on the above data. 



Common Salt, 1 to 305 



Gypsum, 1 to 8,306 



Carbonate of Lime, 1 to 11^,286 



Perchloride of Iron,* 1 to 522,000 



These numbers shew that chloride of calcium is nearly twenty-three times 

 as effective as common salt. Skey estimated it as only twice as effective. 

 Schloesing, as will be stated immediately, estimated chloride of potassium 

 as of only one-fifth of the efficacy of lime salts and chloride of sodium 

 * On referring to my Note Book I find that in July 1866, I had come to the con- 

 clusion that about 1 of Perchloride of Iron is sufficient to precipitate the mud from 

 125,000 of water by standing over night, an approximation at least to the small quantity 

 I have recently found to be sufficient. This was when I was not thinking of its applica- 

 tion on the large scale nor searching for a minimum. 



29 



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