This article is intended to be incomplete. The conversions included in the chart are those I have found to be the most common and most useful in my compounding of formulas. Additional entries could be made. I invite correspondence that could further extend the use-fulness of the chart. If there is a sufficient number of generally useable conversions received, another article summarizing these in chart form will be prepared.
A word of CAUTION. Some conversions can be made without any difficulty or change in the chemical action of a solution - while others simply MUST NOT be made. There are many factors that must be considered. Some compounds are more soluble than chemically-similar alternates. Others are more toxic, less stable, more expensive, difficult to obtain, contain undesirable impurities in its commercial form if not specifically prepared for photographic purposes, etc.
The chart entries have been limited to easy conversions. Those that are NOT recommended for ALL applications are indicated by an asterisk next to the Specified Ingredient. The others are recommended under MOST conditions. There are very special applications where normally useable substitutions must not be used. For example, in preparing dry-packaging of fixer, the crystal form of Sodium Thiosulfate must not be used in place of the anhydrous form. This particular restriction applies to similar forms of chemicals used in dry-packaging.
Producing the necessary alkalinity for photographic solutions can be perplexing.
It is possible to produce the required alkalinity in some solutions by the use of a
small amount of a highly caustic compound like Sodium Hydroxide, or by the use of a
large amount of a milder caustic compound like Sodium Carbonate or Kodalk or Sodium
Phosphate, Tribasic, or others. Does it really matter what is used as long as the
degree of alkalinity reached is the same? It DOES matter:
Photographically speaking there are different families of Alkaline Agents.
Within each family substitutions can be made with little fear of altering the
characteristics of the solution. Some replacements between families mav be
possible but these are the rare exceptions and they are wholly dependent upon the
actual use of the solution. Even within a family there may be limitations on
substitutions. The only way to be absolutely certain as to the advisability of any
substitution is to perform an experiment with the specified agent in one solution
and its substitute in another, and examine the results obtained on identical film
or paper exposed under the same conditions. If nothing drastic occurs and the
results are identical, then you can substitute without any further hesitation. If
the substitute produces better results than the original, then you've made a
fortuitous discovery and'should share it. Again, I invite correspondence on such
discoveries.
The Alkaline families are separated from each other on the chart. The order of entries in the table is based on frequency of use. For all practical purposes, anhydrous and dessicated forms are considered to be the same.
| YOU HAVE | AND THE FORMULA SPECIFIES | MULTIPLY SPECIFIED AMOUNT BY |
|---|---|---|
| Borax (Sodium Borate, Pentahydrated) | Borax (Sodium Borate, Decahydrated) | 0.76 |
| Borax (Sodium Borate, Decahydrated) | Borax (Sodium Borate, Pentahydrated) | 1.31 |
| Sodium Carbonate, Monohydrated | Sodium Carbonate, Anhydrated | 1.20 |
| Sodium Carbonate, Crystal | 2.33 | |
| Potassium Carbonate, Anhydrous* | 0.90 | |
| Potassium Carbonate, Anhydrous | Sodium Carbonate, Monohydrated* | 1.12 |
| Sodium Hydroxide | Potassium Hydroxide | 1.40 |
| Potassium Hydroxide | Sodium Hydroxide | 0.72 |
| Kodalk (Balanced Alkali) (Sodium Metaborate)** | Sodium Carbonate, Monohydrated* | 1.70 |
| Sodium Carbonate, Monohydrated | Kodalk (Balanced Alkali) (Sodium Metaborate) | 0.59 |
| Acetic Acid (Glacial) | Acetic Acid (28%) | 0.28 |
| Sodium Diacetate (Anhydrated) | 0.43 | |
| Acetic Acid (28%) | Acetic Acid (Glacial) | 3.54 |
| Acetic Acid (Glacial) | Sodium Diacetate (Anhydrated) | 1.52 |
| Sodium Thiosulfate (Crystal) | Sodium Thiosulfate (Anhydrated) | 1.57 |
| Sodium Thiosulfate (Anhydrated) | Sodium Thiosulfate (Crystal) | 0.64 |
| Potassium Bromide | Sodium Bromide | 1.16 |
| Sodium Bromide | Potassium Bromide | 0.86 |
| Sodium Acetate (Anhydrated) | Sodium Acetate (Crystal) | 0.60 |
| Sodium Acetate (Crystal) | Sodium Acetate (Anhydrated) | 1.66 |
| Sodium Sulfate (Anhydrated) | Sodium Sulfate (Crystal) | 0.44 |
| Sodium Sulfate (Crystal) | Sodium Sulfate (Anhydrated) | 2.27 |
| Sodium Sulfite (Anhydrated) | Sodium Sulfite (Crystal) | 0.50 |
| Sodium Sulfite (Crystal) | Sodium Sulfite (Anhydrated) | 2.00 |
| Potassium Thiocyanate | Sodium Thiocyanate | 1.00 |
| Sodium Thiocyanate | Potassium Thiocyanate | 1.00 |
| Benzotriazole (Anti-Fog #1) | 6-Nitrobenzimidazole Nitrate (Anti-Fog #2) | 1.00 |
| 6-Nitrobenzimidazole Nitrate (Anti-Fog #2) | Benzotriazole (Anti-Fog #1) | 1.00 |