Correct Forumula for D166?

[ciocc]

The forumula for D166 that I find published at various internet sites is as follows:

Metol: 0.6 gm
Sodium Sulfite: 12.5 gm
Hydroquinone: 4.2 gm
Sodium Carbonate: 12.5 gm
Potassium Bromide: 6.2 gm

The sites don't specify the type of sulfite or carbonate. I have a book published in the UK that specifies the formula as follows:

Metol: 1.15 gm
Sodum Sulfite, anhyd.: 25gm
Hydroquinone: 8.8 gm
Sodium Carbonate, anhyd.: 25 gm
Potassium Bromide: 12.5 gm

Using the conversion factors at www.jackspcs.com, I cannot get the two formulas to match up. A conversion factor would not explain the difference in the two formulas for the bromide, metol and hydroquinone. I tried the "internet" version last night. The print required 1 stop of extra exposure. The image didn't even *begin* to emerge until 3 1/2 minutes and was fully developed in 8 minutes. I also had to bump up the contrast 1 grade. Doesn't sound right to me. I was going to try the other version, but ran out of hydroquinone. I need to order more, but was curious what others have used. That UK book also has the D163 formula, which matches the "internet" versions, except for the Sodium Carbonate. The book specifies 175 gm of Sodium Carbonate (without appending anhyd.). The book only refers to the crystalline and anhydrate versions of it. So I assume the 175 gm is the crystalline version. However, using the conversion factor, I get 408 gm of Sodium Carbonate, Monohydrate. That's outrageous. Is that a misprint in the book?

 

[nworth]

The second formula you list is essentially twice as concentrated as the first. I suspect it is either for double the amount of final solution or for a different dilution. The formulas are essentially the same. My listing for D-166 is the same as your first one. It shows the sodium carbonate as anhydrous but does not tell what kind of sulfite was used. From what you posted, I think we can assume that the sulfite is also anhydrous.

 

[ciocc]

You're right, it's essentially double. Both formulas indicated 1 liter. The problem is the sodium carbonate. I have the monohydrate. To convert from anhydrate to monohydrate, I supposedly multiply by 1.2. That's 30 gms of monohydrate. That's a big difference compared to the 12.5 grams in the 1st formula (although the 1st formula doesn't specify the type). Your listing specifies anhdrate. That's what I needed to know. So I'll try 30 gm of monohydrate instead of the 12.5 gm that I used. Thanks.

 

[ciocc]

Well, you said different final solution or different dilution. You are right. The first formula is for 1:1 dilution. The second formula is for 1:3 dilution. I said 30 grams of sodium carbonate monohydrate, but that's for the second formula. I should use 15 grams with the 1st formula and dilute 1:1 and instead of 1:3. My 1:3 dilution with the 1st formula explains the longer development time.