Sciencemadness Discussion Board

Strontium Carbonate available on-line

Boffis - 30-6-2015 at 19:39

I was recently asked by a friends son if I had any strontium formate, apparently it can be grown into large crystals. I didn't have any but said I could easily prepare some.... famous last words.

I took 50ml of commercial 85% formic acid, diluted with 300ml of water and commenced the addition of strontium carbonate of which I have plenty. I warmed the mixture slowly on a hot plate and used a squeezy water bottle and a stirring rod to wash down and break up the foam. I noticed almost immediately that the foaming died down long before the white carbonate had dissolved. After adding 30% more strontium carbonate than should have been required there was still plenty of free acid in the liquor and a layer of cream sludge about 1cm deep formed when stirring was stopped. I dilute the mixture with an addition 200ml of water just in case the problem was an accumalation of solid strontium formate crystallising on the residual carbonate. But with the volume now over 700ml and the solution at 70-80 C any Sr formate formed should easily have dissolved. I tried to filter the slurry but the filter paper clogged almost immediately. I have now diluted it to over 1 L and left it to settle in a plastic soda bottle. I haven't had time to investigate the materials and residues quantitatively yet but I estimate that the heavy cream coloured sediment that fall to the bottom quickly when stirring is stopped represents about 30% or more of the total quantity added. I suspect this is unconverted strontium sulphate. Basically this material came from too batches one sold as "pyro" grade and the other "ceramic" grade and were purchased from ebay suppliers some years ago. I tested small amounts with dilute hydrochloric acid and also "laboratory GPR" grade from BDH. The latter dissolved completely giving only a slight cloudiness the other two leave much residue. It's hard to analise because the sludge is so difficult to filter.

I would be interested to hear from anyone else who has had this problem and see if this problem is general with strontium carbonate and to warn the unwary.

IrC - 30-6-2015 at 21:03

http://www.ebay.com/itm/STRONTIUM-CARBONATE-1-lb-Pound-Lab-C...

With that title there should be a link. Are you saying the eBay sellers are selling it as carbonate but it is mixed with the sulphate? Also I'm curious if the oxide would be simpler to work with or more difficult. I kilned several pounds of Strontium Carbonate at around 2400 F all day and after cooling put it in containers labeled Strontium Oxide. I was doing experiments making Strontium Aluminate glow powders using various Lanthanide metals as doping, also with the nitrates of metals such as Eu and Dy since they provided action as a flux as well.

Dr.Bob - 1-7-2015 at 05:07

Many chemicals, especially those from overseas and unknown vendors have proven (in my hands) to be filled with crap. We have gotten materials that had sodium sulfate, glass powder, or other cheap fillers added to them. In some cases, it does not matter what the counter ion, so for come pyro purposes, the presence of some sulfate won't matter, as it is the strontium ions that are colored, but even there, having too much impurity can be bad, more so if it is in something like the oxidant, or if the mixture is unstable with certain counter ions. For example, sodium oxalate is used to make yellow colors, but any sodium salt will make yellow flames easily, but most other sodium salts are so hygroscopic as to be bad for the quality of the fireworks made from them, as they suck up water and get crappy. I would ask the vendor for some idea of the purity, grade, analysis or whatever when you buy chemicals off the web or from unknown courses.

Amos - 1-7-2015 at 06:12

Buying oxides, carbonates, or any other naturally-occurring compounds from ceramics suppliers is generally a bad idea, as they've often been produced directly from an impure mineral mined on an industrial scale(this I found out while having a chat with the owner of one such supplier, as she had data on which mines they were getting chemicals from). I suspect part of the reason their products are so cheap is because extreme purity really just isn't a requirement for making pottery at home.

Boffis - 1-7-2015 at 08:03

This is certainly not my first experience of "dodgy" purity some years ago I purchase some "high purity" cobalt sulphate from a UK ebay supplier. The material was crystalline but brownish and contained a lot of pinkish dust. From the colour I suspected iron contamination and decided to recrystallise it. I found the material to be contaminated with ground gypsum (about 8%) and an amorphous inorganic gel like material (about 2% possibly a clay mineral). The later was insoluble but a little gypsum tended to dissolve so requiring several recrystallisations. Interestingly the the nickel and iron content were extremely low as advertised.

I had not expected the strontium carbonate to be lab grade but 30% or more insoluble is very poor quality indeed. I bought some strontium oxide from the same supplier that I purchase the cobalt sulphate from. It was a fine slightly creamy grey powder but it is better quality in that it contains less insolubles and is easily converted into gleaming white strontium hydroxide hydrate by simply treating with water and filtering.

IrC - 1-7-2015 at 23:02

Quote: Originally posted by Amos  
Buying oxides, carbonates, or any other naturally-occurring compounds from ceramics suppliers is generally a bad idea, as they've often been produced directly from an impure mineral mined on an industrial scale(this I found out while having a chat with the owner of one such supplier, as she had data on which mines they were getting chemicals from). I suspect part of the reason their products are so cheap is because extreme purity really just isn't a requirement for making pottery at home.


I looked at the page on wiki and saw this "Other than the natural occurrence as a mineral, strontium carbonate is prepared synthetically in one of two manners. First of which is from naturally occurring celestine also known as strontium sulfate (SrSO4)".

https://en.wikipedia.org/wiki/Strontium_carbonate

So I would think your explanation is correct, they did not worry all that much about purity and the Celestine answers the question in my mind about the source of the Sulphate in the first post in this thread. Good to know these things I had not before considered studying the manufacturing process for various chemicals. This caused me great trouble years ago when I was making glow powders as various batches were seriously poisoned causing the glow to cease in seconds after the charging Ultraviolet was turned off. I had to stop trying to save money and use only high quality sources. As well as stop using metal saws to cut my Lanthanide metals the Iron even in microscopic quantities was the worst glow killer (which I wrote about years ago in a thread somewhere on this site).

Hickory - 2-7-2015 at 02:29

Strontium carbonate is available in high purity as a supplement. I've been quite pleased with Purebulk.

stoichiometric_steve - 2-7-2015 at 03:26

If anyone needs any chemicals, ask me first. I can get great stuff at nice prices, ask around!