1840.] The Galvanic Battery, 1153 



With the constant Battery, solutions are always employed in pairs, of 

 which sulphate of copper invariably forms one, and sulphate of soda or 

 dilute sulphuric acid, may be used indiscriminately as the other. A 

 saturated solution of sulphate of copper, or blue stone, is prepared by 

 adding this substance to boiling water till the water ceases to dissolve 

 it, and then allowing the mixture to cool. Should any crystals of the 

 blue stone be deposited during the cooling, it is a satisfactory proof 

 that the solution is fully saturated ; if no such deposit takes place it is 

 advisable to add more of the salt to the water. A simple method of 

 ascertaining, during the progress of preparation, whether the solution 

 has reached the point of saturation, is to place a single drop on a piece 

 of glass, and mark if minute crystals, or solid matter, are immediately 

 deposited, if so, the addition of blue stone may be discontinued. The 

 proper strength will readily however be estimated after a little ex- 

 perience from the intensity of the blue colour of the solution. A pro- 

 portion of one part of blue stone to three parts of water by weight, 

 has been found by experiment to be most effective, and a large copper 

 cooking vessel is perhaps the best utensil for boiling the mixture in. 

 The sulphate of copper is obtained in the bazaar under the name of 

 -" Nila tutiya," and at an expense of from five to seven annas per lb. 



The solution of sulphuric acid, or vitriol, hitherto employed in the 

 cylindrical Battery, is made by mixing one part of strong acid with 

 eight parts of water. 



The solution of sulphate of soda, or Glauber's salts, which has been 

 used with the blue water in all the experiments to be stibse- 

 quently detailed, is prepared by dissolving one part of the salts in eight 

 or nine parts of warm water, and allowing the mixture to cool 

 before use. Its native name is " Kari nimuk," and it is obtainable to 

 any extent at the trifling expense of two rupees per maund. 



It is unnecessary to notice the numerous other kinds of solutions 

 which have been proposed, as the preceding are at once effective, 

 abundant, and simple, and will amply suffice for every practical purpose. 



Section III. — Of the Arrangements for bringing the Battery into 

 action^ and the precautions to he observed thereupon. 

 The first step towards bringing the Battery into action after all 

 I the preceding details have been completed, is to charge the cells with 



