Sil
Thanks for all the information concerning dichromates.
One small point, when you say that percentage by percentage they should all
produce the same results, strictly this will only be true if they have the
same concentration of the dichromate ion.
Ammonium dichromate has formula mass 252
Potassium dichromate " " 294
Sodium dichromate dihydrate " " 298
So you need a slightly lower mass of the ammonium salt to give the same
concentration of the dichromate ion - or, if you use the same masses, you
would expect the ammonium salt to be slightly faster as it is more
concentrated.
For the same concentration use them in the ratio of the formula masses above
- taking the ammonium salt as 1.00 this gives:
ammonium 1.00
potassium 1.17
sodium 1.18
This is all somewhere in the archive by the way.
Peter Marshall
On Fixing Shadows, Dragonfire and elsewhere:
http://faraday.clas.virginia.edu/cgi-uva/cgiwrap/~ds8s/Niepce/peter-m.cgi
Family Pictures & Gay Pride: http://www.dragonfire.net/~gallery/