882 BULLETIN OF THE BUREAU OF FISHERIES. 



the desired solution fill the container, the volume of the solution may be adjusted 

 with reference to this weight of sulphate, instead of vice versa. 



The relationships of the five factors may now be given in the shape of formu- 

 laries. To use these it is better to reduce the water flow per minute to milli- 

 grams, though the figures may seem unwieldy. This is done by reducing it to 

 liters and multiplying by i ,000,000. 



The proportion (by weight) of the copper sulphate to the water is here desig- 

 nated for brevity and convenience as the "dilution;" e. g., a dilution of i to 

 1 ,000,000, or I ; 1 ,000,000. In formulae and in computing, the figure expressing 

 the copper sulphate is omitted, as, " dilution" = 1,000,000. 



If a is the dilution, and b the water flow in milligrams per minute, then 



— = milligrams of copper sulphate necessary to flow through the siphon every 

 minute. 



If c is the siphon flow in c. c. per minute, then — ;- — = milligrams of copper 



d y\ C 



sulphate which each c. c. of solution must contain. 



If 2 = the number of milligrams of copper sulphate to be dissolved, and 

 y =th& number of c. c. of copper sulphate solution to be in the container at the 



beginning; then 



z yc a yi c 

 If z milligrams of copper sulphate are to be dissolved, r =number 



of c. c. of solution to be made. 



b y. V 

 Or, if y c. c. of solution are to be made, then — —^ = number of milligrams of 



d A. C 



copper sulphate to be dissolved. 



These expressions are put in words as follows: 



Divide the milligrams of ^vater flow per minute by the dilution ; the result is 

 the milligrams of copper sulphate necessary to flo^v through the siphon every 

 minute. 



Divide the milligrams of water flow per minute by the product of the dilution 

 multiplied by the siphon flow in c. c. per minute; the result is the number of 

 milligrams of copper sulphate which each c. c. of solution must contain. 



Multiply together the dilution, the siphon flow in c. c. per minute, and the 

 number of milligrams of copper sulphate to be dissolved ; divide the product by 

 the number of milligrams of water flow per minute ; the result is the number of 

 c. c. of solution to be made. But, if the latter has already been decided upon, 

 and the number of milligrams of copper sulphate to be dissolved is unknown, then : 



Multiply the number of milligrams of water flow by the number of c. c. of 

 solution to be used; also multiply the dilution by the siphon flow in c. c. per 

 minute; divide the former product by the latter product; the result is the num- 

 ber of milligrams of copper sulphate to be dissolved. 



