886 BULLETIN OF THE BUREAU OF FISHERIES. 



It is necessary to avoid leakage from any containers holding the solution 

 in the vicinity of ponds containing fish, since the leak may easily find its way 

 into the ponds. 



Special care should be taken in all the calculations and they should be 

 reviewed before the treatment is begun in order to correct mistakes and to see 

 that all factors have been taken into account. The measuring of the water 

 volumes in fish cans and in the solution container, and the weighing of the sul- 

 phate for this solution, need but ordinary accuracy. The volume of the stock 

 solution and the weight of the sulphate to be contained in it, however, should 

 be determined with special care and accuracy, since the quantities concerned 

 are small and the error is of greater importance. The scales or balances used 

 should weigh to fractions of ounces. 



The difficulty of weighing fractions of ounces in making the stock solu- 

 tion where delicate scales or balances are not available may be obviated by 

 making several times the volume stated, thus using a greater weight of sulphate; 

 or by making the stock solution several times too strong and then properly 

 diluting it. In much the same way portions of the stock solution may be 

 measured in the absence of measures of small volumes. The least conveniently 

 measurable portion should be taken, diluted accurately, the proper portion of 

 the dilution used, and the rest thrown away. 



The cost of commercial copper sulphate is about lo cents per pound in 

 small quantities and about 8 cents in large quantities. It is in the form of 

 crystals, which contain five molecules of water of crystallization. This fact is 

 expressed by the chemical formula CuSO^-l-sHjO. The weight of these crystals 

 is therefore made up of about 36 per cent water. No account is taken in this 

 paper of this water of crystallization. All references to copper sulphate, or to 

 the strengths of solutions of copper sulphate, or to the dilution, are based upon 

 the crystallized commercial substance consisting in part of water. The actual 

 amount of the anhydrous chemical compound, copper sulphate, actually con- 

 tained in the solution, in the dilution, etc., is about 64 per cent of the amounts 

 stated. This fact interferes in no way with the calculations used for the treat- 

 ment herein proposed. In quantitative chemical calculations, however, it is 

 necessary to take account of the water of crystallization. 



Clean rain water, or distilled water, is better for making the stock solution 

 than spring or creek water. 



The sulphate is best dissolved by suspending it in a burlap or loose-meshed 

 bag near the surface of the water in the container. It then dissolves rapidly 

 and without attention, the heavier solution tending to sink. Stir thoroughly 

 after all crystals are dissolved. If the crystals are at the bottom of the con- 

 tainer they dissolve very slowly unless constantly stirred. 



