The DARKROOM COOKBOOK, Third Edition

326 THE DARKROOM COOKBOOK
COMPOUND CONVERSIONS
Although 1.0 ounce equals 28.35 grams the conversion between U.S. Customary and metric
amounts is not equivalent. This is because a liter is slightly more than 32.0 ounces (1.0 quart).
This means that it takes 30.0 grams in 1.0 liter to make the same working strength solution as
1.0 ounce in 1.0 quart. Therefore, if you need to convert a U.S. Customary formula into a metric
formula, or the other way around, you need to compound the amount of chemical used in
order that the percentage of chemistry remains the same in both formulas.
The following dry and liquid tables will help you to quickly make compound conversions.
Any amount not found in one of the tables can be converted by using one of the compound
conversion formulas given below.
Grams/liter � 14.6 � grains/32 ounces
Grams/liter � 0.03338 � ounces/32 ounces
Grams/liter � 0.002086 � pounds/32 ounces
The following compound conversion formulas can be used to convert from U.S. customary
to grams/liter:
Grains/32 ounces � 0.06847 � grams/liter
Ounces/32 ounces � 29.96 � grams/liter
Pounds/32 ounces � 479.3 � grams/liter
The following compound conversion formula can be used to convert liquid measures
from metric to U.S. customary:
ml � 0.032 � fl ounces
The following compound conversion formula can be used to convert liquid measures
from U.S. customary to metric:
fl ounces � 31.25 � ml
The smaller the amount, the more critical it is to be accurate. For example, the difference
between 100.0 grams of sodium sulfi te and 101.0 grams is an error of 1%. The difference
between 1.0 gram of sodium sulfi te and 1.1 grams is a 10% error.
Dry Measure Compound Equivalents
The tables in this section, one for dry measures and the other for liquids, show the conversions
for many of the most commonly used amounts, from metric on the left to U.S. customary
on the right.
Grams � Grains
0.1 � 1.5
0.2 � 2.9
0.25 � 3.7
0.3 � 4.4
0.4 � 5.8
0.5 � 7.3
0.55 � 8
0.6 � 8.8