 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| PhotoKB HomeDiscussion Groups Digital Photography Digital PhotoDSLR CamerasZLR CamerasPoint & Shoot CamerasFilm Photography 35 mmLarge FormatMedium formatDarkroomFilm and LabsOther EquipmentPhoto Technique Nature PhotographyPeople PhotographyTechnique GeneralGeneral Photo Topics General TopicsAustralian PhotographyUK PhotographyDirectoryPhoto Clubs |
Photo Forum / Film Photography / Darkroom / December 2004Moisture
I have a sealed container of Potassium Bromide. The contents of my container are about 50% fine powder and 50% big lumps. The MSDS says this stuff is hygroscopic. Due to the lumpiness of the contents, I'm concerned that the stuff has absorbed enough water to make measurements by weight inaccurate. Am I concerned about nothing? If this is a problem, is there a practical way to remove the water, some process that doesn't require a pro chem lab? TKS Natch > Am I concerned about nothing? If this is a problem, is there a practical > way to remove the water, some process that doesn't require a pro chem lab? Grind it back to a powder with a mortar and pestle.  SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 >> Am I concerned about nothing? If this is a problem, is there a practical >> way to remove the water, some process that doesn't require a pro chem lab? > > Grind it back to a powder with a mortar and pestle. No effect on the measured weight if I simply put it back to powder? Natch > No effect on the measured weight if I simply put it back to powder? I guess it depends on what the standard volume for a measured weight increment is,...that is how much water it has collected. I would perhaps put it next to a dehumidifier for a day or so. You could probably gently heat it with ventilation if its real saturated but thats what i would do and I am not advising beyond that, as there are better more knowledgeable than myself. Maybe Richard K or Patrick Gainer will answer your question better. My experience though, tells me slight clumping is not a major concern with Potassium Bromide and most photo formula. SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 > I have a sealed container of Potassium Bromide. > The contents of my container are about 50% fine [quoted text clipped - 7 lines] > is there a practical way to remove the water, some > process that doesn't require a pro chem lab? I've exactly the same problem. "When It Rains It Pours", Morton Salt, has a built in cure. Calcium chloride is so hygorscopic that it will disolve. I think the phenomena somewhat commen with the halides and a group or two of the periodic table's elements. Way short of a pro-chem-lab solution would be a desiccator. My hunch is that very low levels of moisture will prevent cakeing. Drierite and Silica Gel are two compounds which may be regenerated. I've sources for the two if you're interested. Now that the subject has been brought up, I will look into the matter further. Dan > ... will prevent cakeing. Drierite and Silica Gel > are two compounds which may be regenerated. Dan I've read that 110 C will dry it. I think I'll put my KBr in a small wide mouth and that in a large wide mouth with one of the above desiccants. Dan > I have a sealed container of Potassium Bromide. The > contents of my [quoted text clipped - 13 lines] > TKS > Natch I don't know how much of a problem this is with bromide but it can be for carbonate. You can dry it by heating it gently on a pan. Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com dry a small amount in an oven in 130°C for one hour. cool in a closed jar. * *I have a sealed container of Potassium Bromide. The contents of my *container are about 50% fine powder and 50% big lumps. The MSDS says this *stuff is hygroscopic. Due to the lumpiness of the contents, I'm concerned *that the stuff has absorbed enough water to make measurements by weight *inaccurate. * *Am I concerned about nothing? If this is a problem, is there a practical *way to remove the water, some process that doesn't require a pro chem lab? * * *TKS *Natch * *----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- *http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups *----= East and West-Coast Server Farms - Total Privacy via Encryption =---- I have successfully solved this problem by microwaving in a glass container at low setting. Time is dependant on amount of water requiring removal, but the process is faster than using an oven. > dry a small amount in an oven in 130?C for one hour. > cool in a closed jar. [quoted text clipped - 16 lines] > *http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups > *----= East and West-Coast Server Farms - Total Privacy via Encryption =---- > I have successfully solved this problem by microwaving in a glass container > at low setting. Time is dependant on amount of water requiring removal, but > the process is faster than using an oven. The only problem with that is certain chemicals don't play nice in the microwave, i.e metallic compounds, possibly metal salts. SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 cess is faster than using an oven. > The only problem with that is certain chemicals don't play nice in > the microwave, i.e metallic compounds, possibly metal salts. In what way? Metals I can see the problem with but metal salts? (Name one salt that is not a metal salt?) Signaturehttp://www.petezilla.co.uk > cess is faster than using an oven. Cess? > > The only problem with that is certain chemicals don't play nice in > > the microwave, i.e metallic compounds, possibly metal salts. > > In what way? Arching sparks. > Metals I can see the problem with but metal salts? > > (Name one salt that is not a metal salt?) Yeah, Yeah, Yeah- whatever. I just would hesitate putting some stuff in the microwave where I cook my food. Nor am I eager to find out the possible negative effects of heating chemicals this way. SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 > > cess is faster than using an oven. > [quoted text clipped - 14 lines] > the microwave where I cook my food. Nor am I eager to find out the > possible negative effects of heating chemicals this way. Actually, I'd be concerned the microwave radiation might somehow interact chemically. Not being a chemist I don't know if it could affect the chemical structure but I do know I dry my test prints in the microwave and the silver rich emulsion does not catch on fire :) > -- > LF Website @ http://members.verizon.net/~gregoryblank [quoted text clipped - 3 lines] > is not only unpatriotic and servile, but is morally treasonable > to the American public."--Theodore Roosevelt, May 7, 1918 ------------------------- *(Name one salt that is not a metal salt?) hydrazine salts, hydroxylamine salts, ammonium salts :) *I have successfully solved this problem by microwaving in a glass container *at low setting. Time is dependant on amount of water requiring removal, but *the process is faster than using an oven. * have you noticed that microwaved KBr is reducing grain and ISO400 films look more like ISO 100? ;-{) Just from a practical point of view. Do you really care? The amount of water absorbed by the solid will be at most several percents of its original weight (if you have really bad luck maybe even 20%). However, do you ever need an accuracy of the used amount within a few percents? For example, a recipe which calls for 1 gram of KBr also will work with 0.9 or 1.1 grams. So I would suggest, to take a few percent more than the recipe calls for. Any recipe which is supercritical with respect to used amounts must be regarded as a bad recipe. Wilco > Just from a practical point of view. Do you really care? That's my basic concern. Should I? > The amount of water absorbed by the solid will be at most several > percents of its original weight (if you have really bad luck maybe even [quoted text clipped - 4 lines] > supercritical with respect to used amounts must be regarded as a bad > recipe. Good point. TKS, Natch It's too easy to keep KBr dry using the desiccator I've mentioned to let it vary, say, twixt 30 and 70 percent H2O. Dan > It's too easy to keep KBr dry using the desiccator I've mentioned > to let it vary, say, twixt 30 and 70 percent H2O. Dan Looks to be simpler than regularly baking the stuff, which is what I've done already. It works. Now I'll keep the KBr dry with dessicant. Natch > > It's too easy to keep KBr dry using the desiccator I've mentioned > > than to let it vary, say, twixt 30 and 70 percent H2O. Dan > > Looks to be simpler than regularly baking the stuff, which is what > I've done already. It works. Now I'll keep the KBr dry with dessicant. If the desiccant method works well the KBr is always dry. Of course the desiccant will need regenerating. The percent moisture content otherwise will vary with humidity. I've no idea the hygroscopic potential of KBr but at least calcium chloride is so hygroscopic it will dissolve. This is a matter I've been putting off so will be following up. Dan KBr is very well soluble in water, hence even small amount of water will cause clumping of fine powdered salt. However, KBr is nowhere as bad as calcium chloride. Well closed (original)jar should do. You open it for weighing, you close it right afterwards. No problem. Disregard few percent of moisture. * *RE: Mr. Natchul wrote: *> *> > It's too easy to keep KBr dry using the desiccator I've mentioned *> > than to let it vary, say, twixt 30 and 70 percent H2O. Dan *> *> *> Looks to be simpler than regularly baking the stuff, which is what *> I've done already. It works. Now I'll keep the KBr dry with *dessicant. *> * *If the desiccant method works well the KBr is always dry. Of *course the desiccant will need regenerating. *The percent moisture content otherwise will vary with humidity. *I've no idea the hygroscopic potential of KBr but at least *calcium chloride is so hygroscopic it will dissolve. *This is a matter I've been putting off so will *be following up. Dan > KBr is very well soluble in water, hence even small amount of water > will cause clumping of fine powdered salt. However, KBr is nowhere [quoted text clipped - 8 lines] > *> > 70 percent H2O. > *> Disregard; pay it no attention. Not so bad as CaCl2. Damp is too wet in my book and not knowing how damp, and the hassel of drying and reweighing to find out is more of a bother than necessary. Here is another solution. KBr in solution. Dry and weigh a years worth then dissolve. BTW, my text mentions only deliquesce. Dan |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.