[Alt-photo] ammonio-nitrate

jimbobnola at cox.net jimbobnola at cox.net
Fri Sep 16 17:01:30 UTC 2016

Hi Chris,
Glucose is a reducing sugar.  It is a reducing agent in an alkaline enviroment with heat.  It reduces the Ag+ ion to Ag (silver metal).   It also reduces a copper II sulfate solution to copper I oxide (a yellow precipitate) which is the basis of Fehling's Test  and Benedict's Test for urine sugar.  A commercial version for diabetics used to be available in pharmacies as Clinitest tablets.  
---- "Christina Z. Anderson via Alt-photo-process-list" <alt-photo-process-list at lists.altphotolist.org> wrote: 
> Well, Jim there you have it. 
I have no desire to make a process more complex just for historic purposes when it is a) not necessary and b) dangerous. Because if there is a mistake to be made, a student will do it.
Thanks for this!
But I’m dying to know why glucose plated out the silver?

On Sep 16, 2016, at 10:41 AM, Jim Patterson via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org> wrote:

> Hi Chris & all, 
> A word of caution.  Ammonia + silver nitrate can produce silver fulminate which is very explosive and very sensitive to jarring, heat.  We used to do the "silver mirror" test for glucose in the urine (back in the old days).  It was done by adding a ml of silver nitrate solution to a test tube, then drops of ammonia until the brown precipitate first formed dissolved, then a ml of urine was added and it was heated over a bunsen burner.  If glucose was present, the silver plated out on the bottom of the test tube.  We were warned not to mix up a stock solution and to always wash the waste down the drain promptly with a lot of water.  Once a lazy student let it sit in the test tube rack until next lab when it had evaporated to dryness.  The student dropped the tube in the sink and it exploded.  Fortunately no one was hurt.
> Jim Patterson
> ---- "Christina Z. Anderson via Alt-photo-process-list" <alt-photo-process-list at lists.altphotolist.org> wrote: 
>> I’ve compiled some notes, so bear with my truncated note taking skills, but here is some stuff on ammonio-nitrate which spellcheck seems to want to change to ammonia.
> I was planning on trying it out, but I just don’t see a reason to make the silver nitrate formula more complex than just adding silver nitrate to water.
> Citric acid was added often, in fact about 30% of the 80 formulas I recorded have added citric. But I also don’t see a need for that, especially if citric acid or sodium/potassium citrate are used in the salt formula. Someone may convince me differently though, but Young agrees. 
> The paper that turns brown for me is invariably the plain salted ones with no citrate. The others stay unfogged for the whole day and even into the next, but then again I am not silvering 100 sheets for the week like they probably did back in the day when paper keeping was a big deal.
> Chris
> 1854 JPS Vol1 “Hints on Positive Printing” pp. 170–171 by W. Teasdale. Why ammonio-nitrate is objectionable. It cannot be used with albumen. It has to be washed before being fixed. Have to take great care to wash fingers after handling or brown stains will occur. The paper won’t keep. 
> Howlett 1856 p. 12 The ammonio-nitrate was first described by Taylor. It is quicker and it prints black and white more easily. Formula is on this page.
> Sparling 1856 pp. 153–166 1gr gelatin, 10grs am or sod chlor water 1 oz. Then use the normal silver solution of 60grs/1oz or the ammonio nitrate solution (which he gives a formula for here; he also says that if the brown precipitate never forms it is because there is a lot of nitric acid in the solution and it would require therefore lots of ammonia to get the precipitate but this doesn’t happen frequently. Also, all say to keep ammonio-nitrate in a dark place because it is more prone to reduction than silver nitrate. Also, that brush is better than tray because by tray the ammonio-nitrate reacts with the salt and produces reddish pink half-shadows. Also, oddly, that ammonio-nitrate paper doesn’t keep but a few hours whereas gelatin/silver nitrate paper keeps a few days).
> 1868 Illustrated Ph Printing on Mat Paper by George Dawson pp. 359–360. He dismisses ammonio-nitrate paper.
> Harrison History 1888 p. 83 1842 ammonio-nitrate Dr. A. S. Taylor (and A. Smee and Mr. Collen about the same time) which cannot be used with albumen because it dissolves the egg white.
> 1908 American Photography Thomson, James Vol II No. 3 March 1908 Plain Salted Paper pp. 121–126  He says that ammonio-nitrate is used to make the paper more sensitive and to give richer prints, but the paper doesn’t keep longer than 24 hours and it is best to use the fuming method instead.
> Reilly 1980 64 the ammonio-nitrate bath was very popular 1840–1860 but it had some disadvantages: prints yellowed quickly and the solution discolored quickly. It also dissolved the albumen off the paper. It also produces “fulminating silver” which is explosive if a solution is boiled down. 
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