The temperature of the water in which the chemicals are being dissolved has a great deal to do with the
speed at which they are dissolved. The temperature should be that which is prescribed in the particular
formula being used.
Preparation of percentage solutions of dry chemicals:
To prepare correctly a 10% solution of any dry chemical, dissolve 1 ounce of the chemical desired in 8
ounces of water; then add water to make 10 ounces.
EXAMPLE: If a formula calls for 2 ounces of a 10% solution of potassium bromide, dissolve 1 ounce
of potassium bromide in 8 ounces of water, then add water to make 10 ounces. Measure out 2 ounces
of this solution for the formula. There are many times when it is desired to have more or less than a
10% solution or more or less than 10 ounces of the solution. In these cases, it will be found to be more
desirable to use the following formula:
To have the answer in ounces: Multiply the amount desired in ounces by the percentage desired
as a decimal.
To have the answer in grains: Multiply the above answer by 440. (There are actually 437-1/2
grains to an ounce, but to simplify math formulas, we use 440 grains as an ounce.)
Preparation of a percentage solution of liquid chemicals:
Multiply the amount desired by the percentage desired; divide this product by the percentage on hand.
EXAMPLE: A formula calls for 32 ounces of 28% acetic acid. Glacial acetic acid (99 1/2%) is the
chemical on hand.
32 times 28 = 896 = 9.0 ounces of 99 1/2%
99.5
99.5
Add 9.0 ounces of 99 1/2% glacial acetic to 23 ounces of water to obtain 32 ounces of 28% solution of
acetic acid.
Stock solutions: A stock solution is a solution in a concentrated form. It must be diluted for proper
use.
Replenisher solutions: A replenisher solution will not revive an exhausted developer solution. A
replenisher solution is used mainly to maintain the desired level of the developer solution. It helps to
prolong the life of a developer.
22
Previous Page
