Silverprint (UK) Borax

[Alan Johnson]

http://www.silverprint.co.uk/HSPDF/sodium-tetraborate.pdf
This appears to be the anhydrous form CAS 1330-43-4
Am I right in thinking that formulae are generally given referring to the decahydrate CAS 1303-96-4 ?
Thanks.

 

[Pgeobc]

Read the formula, because some assume one form and some the other. However, the decahydrate can be converted into anhydrous by calculation. The factor is: divide the anhydrous by 0.85 to get equivalent decahydrate. Conversely, multiply the decahydrate by 0.85 to get the equivalent amount of the anhydrous form.

The person who published the formulas for Caffenol-CM and its variations, http://caffenol.blogspot.com/ , specifies weighed amounts of the anhydrous form. Others use teaspoons of the hydrated form.

 

[Ian Grant]

Ask Martin Reed at Silverprint he's very helpful.

I'm used to buying Borax by the metric ton from Consolidated Borax (Ten Mule Team) and that's Decahydrate which is the common form used in most formulae and industry.

Ian

 

[jochen]

Hello,
I think I have to correct the factor: The molecular weight of the decahydrate is 381, the anhydrous form has 201 (= 381 minus 10 x 18). So if you have anhydrous borax and the formula is for decahydrate, you have to multiply the decahydrate amount by 0.53. (201/381 = 0.53)

 

[Alan Johnson]

I received this by email from Silverprint:
"....we sell DECAHYDRATE type of sodium tetraborate (Borax).As you pointed out it does not say this on the Coshh form.We will be changing this on our website and thanks for pointing this out."
Thus the link I provided to the Coshh form is to be corrected.Silverprint actually sell the decahydrate which according to the Film Developing Cookbook and the Darkroom Cookbook is,I believe, the type usually meant in formulas referring to Borax..