bad silver nitrate ?

[smieglitz]

A few months ago I was given an ounce of silver nitrate reagent from who knows how long ago. I suspect it is at least 30+ years old. When I opened it the other day I saw the crystals had turned gray in color. I'm wondering what might be the reaction involved that would cause this. I've used bottles of silver nitrate that were probably 100 years old but the crystals were still white even though they had fused together. The oldest stuff was stored in amber glass but the newer bottle is a plastic.

I'm thinking of just mixing it up to about 9% solution, leaving it out in the light to "sun" for a day and then filtering it to remove any organics if that is what has caused the darkening. I'd like to use it for wetplate but don't want to contaminate my present sensitizing bath if the impurities can't be removed.

Any other ideas on what the contaminant might be and how to purify the silver nitrate again?

Joe

 

[Dana Sullivan]

I'd suspect that the crystals will be fine. If you disolve them, and the solution is clear, then you know they're fine. Any form of contamination is most likely going to cause the solution to turn cloudly immediately. You could probably let the contaminants settle and then pour the clear solution off the top.

The price to frustration ratio runs in favor of price in this case. 30g of silver nitrate runs a little over $30, so the labor involved in purifying and reclaiming a small amount doesn't make economic sense. If it were 30g of Potassium Chloroplatinite at $30 a gram, on the other hand, it would make perfect sense!

 

[chrobry]

Joe,
this is normal that silver nitrate gets grayish after some time. At least for some purposes it is considered bad. Apart of photography I use silver nitrate at work to stain protein gels, I am not going into details here. When the reagent gets this gray color we discard it. But it might still be fine for printmaking. I am not sure here as for praintmaking I buy silver intrate in the solution form for a long time now. Just try, but do not e surprised if it did not work.

regards,

Jan

 

[JG Motamedi]

Joe,

I picked up 6lbs of very old "Eastman-Kodak" branded silver nitrate a few years back. It was quite gray but worked perfectly.

 

[smieglitz]

Thanks for the responses everyone. I think I'll use it for Van Dyke Brownprints or albumen rather than taking a chance that it could be added to the collodion sensitizing bath.

Joe

 

[lonelyboy]

If the silver nitrate turn grey, it may have been photo decomposed into silver already.

 

[Jordan]

I second Lonelyboy. And might add that "sunning" it will increase the problem. Silver salts are light sensitive (some more than others).

 

[smieglitz]

Jordan,

Can you provide more detail on why you believe sunning to be a deleterous process?

It has been my practical experience that a silver nitrate solution is not adversely affected by exposure to light. In practice, I load the tank and drain and filter it in light, sometimes the brilliant light of day outside.

Silver nitrate certainly seems to react readily in the dry state when in contact with organic material (e.g., paper, leather, gelatin, albumen, etc.) even under safelight conditions or in the dark. But, simple exposure to light has never darkened the solution IME.

Just curious about the chemistry...

Thanks,


Joe

 

[Jim Noel]

Silver nitrate becomes light sensitve when in contact with organic substances - at least that was what I was taught many years ago.

 

[smieglitz]

Silver nitrate becomes light sensitve when in contact with organic substances - at least that was what I was taught many years ago.

Apparently a pure solution of AgNO3 is not light-sensitive, at least according to John Towler's The Silver Sunbeam (the bible of wetplate collodion photography) from which I quote:

"If the bath is impoverished, it will at the same time be contaminated. The remedy is to boil it some time in a glass flask in order to get rid of the ether, alcohol, and the volatile substances produced by decomposition, as also to coagulate organic matter; then allow the bath to cool, and filter. To the filtrate add more nitrate of silver if required. Placing an old bath in the sun for several days is also of great assistance, but it is far from being equal to boiling or distilling." -ch XLIV

"It is advisable, therefore, to expose the bath in a glass vessel to the rays of the sun as often as possible, in order that the organic matter may be precipitated... This exposure to the rays of the sun, and frequent filtration will remedy in a great measure the trouble alluded to, and there is no fear of injuring the property of the solution, for nitrate of silver alone is not acted upon by light, does not change at all when pure." - chXV

Joe

 

[Tom Taylor]

I'd suspect that the crystals will be fine. If you disolve them, and the solution is clear, then you know they're fine. Any form of contamination is most likely going to cause the solution to turn cloudly immediately. You could probably let the contaminants settle and then pour the clear solution off the top.

The price to frustration ratio runs in favor of price in this case. 30g of silver nitrate runs a little over $30, so the labor involved in purifying and reclaiming a small amount doesn't make economic sense. If it were 30g of Potassium Chloroplatinite at $30 a gram, on the other hand, it would make perfect sense!

At one time B&S supplied SN in brown glass bottles and I never had a problem. Then they switched to white plastic bottles in which SN will slowly turn grey. Upon disolving the grey SN crystals in distilled water the solution is clear but I found the brush overcoats on paper are the same grey color as the grey crystals. I reported the grey crystals to Melody and she apparently consulted with you and the reply was that B&S had no knowledge that SN turned grey in the plastic bottles.

Thomas