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This is the type of Sodium Thiosulfate Anhydrous you need in order to make Silver Thiosulfate for STS spray, which is used in making feminized seeds.
This is Na2S2O3.
Don't use the more common Na2S3O4 by the same name. It doesn't work well for the STS, and is a different molecular weight.
It has an extra Sulphur and oxygen molecule, and a molar mass of 206.1721 not 158.098.
I wasted months before I realized this was my problem with my earlier STS experiments.
See the bottom for my personal STS recipe. I also have pre made kits available.
This 30g (1ounce) bottle of sodium thiosulfate is in anhydrous form, meaning it contains no water. Take a look at the table below to discover the sodium thiosulfate formula, the density of sodium thiosulfate, its shelf life, and more!
Formula Na2S2O3
Formula Weight 158.098
Grade Reagent
Form Crystalline
Density 1.667 g/mL
CAS # 7772-98-7
Classification Non-Regulated
Storage Code Green
Shelf Life 12 Months
Alternate Names
Photographic Hypo, Sodium Hyposulfite
My STS recipe:
To make 100ml of concentrated STS solution of .02M or 20mM-
(Always add Silver Nitrate solution to the Sodium thiosulfate solution while stirring rapidly within 30 seconds)
Use only Distilled water.
To make 100ml concentrate STS:
Measure, and dissolve 1.264g Sodium Thiosulfate anhydrous in 80ml water,
and in a separate container,
mix .34g Silver Nitrate in 20ml water.
Once dissolved, Add the Silver Nitrate solution to the Sodium Thiosulfate solution while stirring rapidly within 30 seconds.
Use only Distilled water!
To dilute, and make the 3mM plant spray:
400ml
Add 60 ml of concentrated stock solution to 340ml of distilled water.
200ml (8oz bottle)
Add 30 ml concentrate to 170ml water.
100ml
Add 15 ml concentrate to 85ml water.
The STS can be stored in the refrigerator for up to a month. However, preparation of the STS is best just prior to use.
*This contains no Silver Nitrate. *
You'll need to buy that separately. It's cheap.
I also have full STS kits available for sale if you don't want to mess with making your own
Happy breeding, and Thanks for all the support!