Amazon has the necessary chemicals, I keep hearing about people getting out on a watch list for ordering sodium nitrate, but we're not using a bunch of this stuff. A pound of it will last a lifetime for what we're doing.
You don't need sodium nitrate but silver nitrate and 10g is around $50. It's the stuff that goes black when exposed to light and is used for black and white film.
PREPARATION OF SILVER THIOSULFATE (STS) SOLUTION
Silver Thiosulfate (STS) is commonly used to block the action of ethylene in plant cell cultures.
Ethylene is a hormone that is present in the gaseous state. Ethylene increases during senescence and ripening, and has been shown to increase in plant cell cultures due to wounding or the presence of auxins. Silver nitrate may be used alone to block the action of ethylene but it is not transported as well as STS thus is seldom used alone.
Prepare a 0.1 M Sodium Thiosulfate (STS) stock solution by dissolving 1.58 g of Sodium Thiosulfate (Product No. S 620) into 100 ml of water.
Prepare a 0.1 M Silver Nitrate stock solution by dissolving 1.7 g of Silver Nitrate (Product No. S 169) into 100 ml of water. Store the stock solution in the dark until needed to prepare the STS.
The STS solution is prepared with a molar ratio between silver and thiosulfate of 1:4, respectively. Nearly all of the silver present in the solution is in the form of [Ag (S2O3)2] 3-, the active complex for ethylene effect inhibition.
Prepare a 0.02 M STS by slowly pouring 20 ml of 0.1M silver nitrate stock solution into 80 ml of 0.1 M sodium thiosulfate stock solution. The STS can be stored in the refrigerator for up to a month. However, preparation of the STS just prior to use is recommended.
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Then there's this one that uses different ratios of the precursor chemicals.
Preparation of STS:
First, a stock solution is made. It consists of two parts (A and B) that are initially mixed separately, then blended together. Part A is ALWAYS mixed into part B while stirring rapidly. Use distilled water; tap water may cause precipitates to form.
Wear gloves while mixing and using these chemicals, and mix and use in a properly ventilated area. A mask will prevent the breathing of any dust, which is caustic. STS is colorless and odorless, and poses minimal health risks if used as described here. (See material safety data sheet links below). Note that silver nitrate and STS can cause brown stains upon drying, so spray over newspaper and avoid spilling.
Part A: .5 gram silver nitrate stirred into 500ml distilled water
Part B: 2.5 grams sodium thiosulfate (anhydrous) stirred into 500ml distilled water
The silver nitrate dissolves within 15 seconds. The sodium thiosulfate takes 30-45 seconds to dissolve.
The silver nitrate solution (A) is then mixed into the sodium thiosulfate solution (B) while stirring rapidly. The resulting blend is stock silver thiosulfate solution (STS).
This stock solution is then diluted at a ratio of 1:9 to make a working solution. For example, 100ml of stock STS is added to 900ml of distilled water. This is then sprayed on select female plants.
Both the stock STS and the working solution should be refrigerated after use, as well as the powdered chemicals, to avoid activity loss. Excess working solution can be safely poured down the drain after use (with ample running water) with negligible environmental impact. It's pretty cheap.
Each liter of stock STS will make ten 1-liter batches of working solution of STS. With the minimum amount of base chemicals ordered from Photographer's Formulary (see link below), this means that each 1-liter bottle of working solution STS costs less than 9 cents, and can treat 15-20 mid-sized plants. That's 200 1-liter batches of STS for $18. Note that the distilled water costs far more than the chemicals.
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Preparation: Sodium thiosulfate can be prepared by heating sulfur with either aqueous sodium sulfite solution or aqueous sodium hydroxide solution.
6 NaOH + 4 S ? Na2S2O3 + 2 Na2S + 3 H2O
Physical properties : Sodium thiosulfate is a white crystalline solid which is odorless and highly water soluble. It has a density of 1.667 g/mL and a melting point of 48.3°C.
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I looked up the molecular wts and noted them here. Now I need to calculate the amounts of each part to use so after the reaction is over none of the original parts is left over. Not a big deal but haven't got around to it yet. Very soon tho.
Mol wts.
Ag = 107.87
Na = 22.99
S = 32.06
O = 15.99
N = 14.00
H = 1.00
Mol wt. of Na2S2O3 = (22.99 x 2) + (32.06 x 2) + (15.99 x3) = 55.98 + 64.12 + 47.97 = 168.07g
Mol wt. of NaOH = (22.99 + 15.99 + 1) = 39.98g
Mol wt. of HNO3 = [1 + 14 + (15.99 x 3)] = 62.97g