TC-1 is a bit more dilute than what we used in the O-Chem lab that basically
omitted the water in the TC-1 recipe. While not dangerous when handled
carefully, it is very reactive. With the Cr, there are more concerns about
carcinogenesis, etc. than when I was in college. It should go without saying:
never pipette by mouth. My father had someone in his chem class who did this
with chromic acid cleaning solution and lost a bunch of teeth at once.
The Sigma-Aldrich site has more good information:
https://www.sigmaaldrich.com/technical-documents/articles/labware/cleaning-glassware.html#ref
1. Chromic acid cleaning solution - Use powdered commercial or technical grade
sodium dichromate or potassium dichromate. If the compound is in the form of
crystals, grind to a fine powder in a mortar. To 20 grams of the powder in a
liter beaker, add a little water, sufficient to make a thin paste. Slowly add
approximately 300 mL of commercial concentrated sulfuric acid, stirring well.
Transfer to a glass-stoppered bottle.
Larger amounts can be made in the same proportions. Use the clear supernatant
solution. Chromic acid solution can be used repeatedly until it begins to turn
a greenish color. Dispose of in accordance with appropriate regulations. Dilute
with large volumes of water before discarding, or carefully neutralize the
diluted solution with sodium hydroxide. Chromic acid solution is strongly
acidic and will burn the skin severely. Use care in handling it.
—Kurt in balmy Sioux Falls, SD
On 3 Jan 2021, at 15:38 , `Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
Here are some formulae for Kodak tray cleaners. From a very old book but
Kodak published them for decades.
Kodak Cleaning Solutions
TC-1
Water...........1.0 Liter
Potassium bichromate......90.0 grams
Sulfuric acid, concentrated....96.0 ml
This solution can be reused many times.
TC=2
Solution A
Water.....1.0 liter
Potassium permanganate....5.0 grams
Sulfuric acid, Concentrated....10.0 ml
Solution B
Water 1.0 liter
Sodium bisulfite 10.0 grams
Pour in solution A and allow it to stand for a few minutes. Then rinse out
with water and pour in Solution B, which will clear the remaining stain.
This formula is especially recommended for removal of silver stains.
S-6 Hand Stain Remover
Solution A
Water 1.0 liter
Potassium permanganate 7.5 grams
Solution B
Water 1.0 liter
Sodium bisulfite. 480.0 grams
Wash hands in solution A, then rinse in water and rinse again with solution
B. Will also remove ink stains.
For cleaning mold and mildew from deep tanks the book suggests cleaning with
calcium hypochlorite. This is available from pool supply stores.
Also recommended for silver deposits is a 1.0% solution of Tri Sodium
Phosphate. This is often available at hardware stores.
From “Photographic Chemicals and Solutions” Crabtree and Mathews (1938)
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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