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Techniques for CollectorsDoes anyone use Salt of Phosphorus Beads these modern times?

21st Mar 2016 17:20 UTCDana Morong

I used to do some blow-pipe analysis and wet chemical tests, along with the usual physical tests, to narrow down possibilities in mineral identification. For this one needs a copy of George J. Brush’s (c.1900) Manual of Blow-Pipe Analysis and Determinative Mineralogy (the editions co-authored by Penfield are just as good); this has been common in the used book market. Although one can get a scanned copy online, what I have seen online had poorly copied pages, so I think a paper copy better even if in poor condition (as long as it is all there). For this subject, I also highly recommend a modern book: Mineral Identification: A Practical Guide for the Amateur Mineralogist, by Donald B. Peck, 2007. This one is available through Mineralogical Record (see book for sale at www.mineralogicalrecord.com in its Books for Sale section).

One of the more interesting aspects of blowpipe analysis is the use of bead tests. These are useful for finding various cations, mostly those of transition elements. However, as certain semi-metals (particularly arsenic) can brittle and ruin platinum wire (used as a support in bead tests), it is wise to first use tube tests (which work well with semi-metals) to identify such, and then if these are absent, use the bead tests. Beads are usually either of borax, soda (sodium carbonate), or Salt of Phosphorus (once called ‘microcosmic salt’). This last is usually harder to obtain, and once I devised a recipe to make it of modern materials (the recipe worked, and I got a precipitate of it, plus a solution useful in another test; neither requiring purity from the other). However, an easier solution is an alternate source: I discovered it by accident several years ago (I was taking college courses at the time, so this was actually more like 20 years ago, but I remember it well as I noted everything down and kept copy of it). My mother had asked me if Bakewell Cream (name trademarked) were cream of tartar. It isn’t, although used to the same purpose in baking. The principle is that one adds a dry acid (in this case either cream of tartar, or Bakewell Cream) and baking soda, both while dry, and only when wet do they start to react with another, releasing carbon dioxide from the baking soda, thus raising the biscuits (my dear old mother still makes good biscuits). B.C. (Bakewell Cream) is actually sodium acid pyrophosphate, plus a little starch, the added starch is possibly to prevent caking of the powder (one can also get it without any starch by contacting the company directly, but I only tried the type with starch).

I wondered if this B.C. (as I call the Bakewell Cream) when fused in the flame, would it fuse to the same reactive sodium metaphosphate as does Salt of Phosphorus (ammonium acid sodium phosphate, hydrated)? So I did a little chemical notation with pencil and paper, and concluded that it was worth a try.

Results were quite satisfactory. As with Salt of Phosphorus, it took several build-ups to get a bead (a hand-lens is useful). It smelt like burnt cake when the starch burns off, but I found that much preferable to the slight ammonia smell that Salt of Phosphorus gives when fused. With B.C. there is excess carbon (from the starch) but I thought that as I couldn’t get a good reducing flame (R.F.) anyway with Salt of Phosphorus, then maybe the carbon would reduce, and get the same R.F. reactions as for Salt of Phosphorus.

I tried various ions, in fact all of those listed in Pough’s Field Guide to Rocks and Minerals, in the Salt of Phosphorus section of bead tests, except for wolfram (tungsten) and titanium, as I didn’t have samples of those in soluble form at the time. I used the oxidizing flame (O.F.) position of the Bunsen burner (propane fuel, with a sort of pressure reduction valve). I found that the starch did reduce, getting all the R.F. (reducing flame) reactions, even when using the O.F. position. Even the manganese oxide came out colorless when a lot was used, and that (R.F. reaction) is normally difficult to get!

The colors seemed to match those in the Salt of Phosphorus – R.F. table in Pough’s book, but for Cold beads only. There was no match for colors when the beads were hot. I wrote it all down as I did the tests, and later sent a copy to Dr. Pough, who at the time was trying to get people to come up with more simple tests, hoping to include in the 5th edition of his book. For the cold bead reducing-flame colors, there was a match between those of Salt of Phosphorus and those of Bakewell Cream. Even the silica skeleton test worked with this reagent.

Those were the results in 1993. If the amount of starch remained the same, it is likely that the results will be similar, but I can make no claim as to the effects of differing amounts of starch, which could affect the reducing ability of the reaction.

The cans are labeled “The Original Bakewell Cream” and although sold in some supermarkets in the New England area, it may not be available other places. The latest address is: New England Cupboard, PO Box 8, Hampden, ME 04444 – and the website is www.newenglandcupboard.com and the telephone 207-848-4900.

If anyone chooses to try this material, I would highly recommend getting two cans of the material, one for the baker in the family, and the other for the mineral chemist, mark them separately and keep them separate. The food one should be kept in the kitchen, and the reagent one kept in the lab (preferably shifted to another container, and relabeled), and never mixed. It is a fundamental rule of chemists (and as important as kosher rules to the Orthodox) never to mix kitchen stuff or food with laboratory stuff, and to label everything and to store it properly. And of course, to wash hands before and after practicing either the culinary arts or determinative mineralogy.

7th Dec 2016 05:49 UTCJohn Attard Expert

Dana

Borax beads are probably more revealing than salt of phosphorus or as you say Microcosmic salt. Actually I have never heard anyone using microcosmic salt. The blue for Cobalt may be hard to equal in other ways.

By the way instead of platinum you may find that Nichrome wire works well and is much less expensive.

Blowpipe analysis in my opinion has long been dead. It requires too much skill and suffers from a lack of reliability.

The wet chemical tests are still usable... I still find them useful even though I have access to XRD and XRF. I do not despise old tests because there are newer ones.

7th Dec 2016 15:14 UTCSteve Hardinger 🌟 Expert

"The wet chemical tests are still usable... I still find them useful even though I have access to XRD and XRF. "

And because we are chemists and like to play with chemicals every now and then?

7th Dec 2016 15:28 UTCD. Peck

John, I don't know whether the nichrome wire I had was inferior or what, but I found that I was consistently getting a light green color in my beads. With platinum, the wire kept getting shorter, and since it is relatively expensive, I looked for an alternative. Carolina Biological Co. sells a bacteriological inoculation wire loop that is sturdy, relatively inexpensive, and has given me good service.

7th Dec 2016 16:24 UTCRonnie Van Dommelen 🌟 Manager

Don,

I searched for 'Carolina Biological Co. bacteriological inoculation wire loop' but those are nichrome. Perhaps different alloys are more/less suitable?

7th Dec 2016 18:06 UTCSteve Hardinger 🌟 Expert

Don, from Wikipedia: "Nichrome (NiCr, nickel-chrome, chrome-nickel, etc.) generally refers to any alloy of nickel, chromium, and often iron and/or other elements or substances. Nichrome alloys are typically used in resistance wire. They are also used in some dental restorations (fillings) and in other applications."

So it might be that cheaper versions of this alloy (but still called Nichrome) may have enough Cu etc to provide false colors, especially when the test is a particularly sensitive one.

7th Dec 2016 18:30 UTCThomas Lühr Expert

What's about using magnesia rods instead of a wire loop ?

7th Dec 2016 19:03 UTCD. Peck

The nichrome wire I was using is from Radio Shack (I think). It is a small spool sold for use as an electrical resistor. In any case, it didn't work.

^Thomas: I have never used magnesia rods, but have seen them suggested in various books. Where are they available? How expensive are they? Can they be re-used?

12th Dec 2016 23:53 UTCDana Morong

"Blowpipe analysis in my opinion has long been dead. It requires too much skill and suffers from a lack of reliability."

Depends on what particular test and also experience of the user.

I recall once in mineralogy lab (in college) that the T.A. said of some tiny waxy orange hexagonal prisms (on a rock, but some had fallen off), that they might be sphalerite or [some other species which was not even hexagonal!]. I don't know whether he planned to run one through the XRD machine (a fascinating machine, and useful for many things, but why use it on stuff one can use simpler tests for). So as several of the tiny crystals were loose, I took one home and put it B.B. (as the old books say), and eventually ended up with a tiny bead of lead. I had already suspected vanadinite, which contains lead. This particular example did not suffer from "a lack of reliability". Rather, there are some certain tests that have proved to be more or less reliable - depending on the particular test - and a few which have been mis-written by some who never tried the subject, but put these 'shortened' versions of tests (in which important steps have been left out - in both wet and dry tests) in a book so that a student who tried such tests upon known materials found that the test failed, then they blamed the whole subject for unreliability. This is like someone who writes a cookbook but leaves out the yeast in a recipe for dough, and then the person trying it finds that it never rises, and concludes that the whole subject is unreliable.

28th Jan 2017 20:14 UTCGeorg Graf

Hi Dana, hi all,

I use Borax salt beads on magnesia rod to test chemical composition of minerals. - After a test, I don´t clean the magnesia rod, but break the part with the bead (some mm long) away. Thus, the magnesia rod becomes a little bit shorter by every test.

Mixing in bleaching agent (for treating clothes in a washing machine) to the Borax, firstly I get oxidating conditions in the molten bead, by the peroxide; followed by reducing conditions, by the organic compounds of the bleaching agent.

Best to all! Georg

10th Jul 2018 03:32 UTCRocky Mineralowicz

I am late to the discussion but in case anyone still cares, the book Identification and Qualitative Analysis of Minerals by Orsino Smith gives color photos of both borax and salt of phosphorus beads in both oxidizing and reducing flames. I have done both but usually just do a borax bead unless I want to get a bit more info. The viscosity is lower with salt of phosphorus beads and they don't stay on the loop as easily as a borax bead. Also, silica dissolves in a borax bead but will leave a skeleton or residue floating around in the hot bead that you can see in a magnifier or keen eye if you don't catch your eyebrows on fire.

My experience with nichrome wire is the same as Donald Peck's. My blank bead always had a greenish tint so I bought a piece of Pt wire but it is very expensive. The inoculation loop that Don recommended sounds like a great inexpensive alternative.

I classify such bead/blowpipe/tablet/flux sort of procedures as "classical mineral analysis". These tests may date back +100 years. I find them of limited usefulness but really enjoy the exercise and sometime gives some added info to the amateur.

10th Jul 2018 17:01 UTCDonald B Peck Expert

Hi Rocky,

Like most collectors, I don't have access to xray, EDS, or any other electronic instruments for analysis and mailing a piece off, while relatively inexpensive, reaches a noticeable total over time. That and (like you) the pure enjoyment of finding my own answers was why I started using the old (some not so old) analytical techniques.

Bead tests and flame tests are easy and don't take much equipment. The chemicals are easily obtained . . . except salt of phosphorous (sodium ammonium acid phosphate or microcosmic salt). At the top of this thread, Dana Marong offers a substitute from the local pharmacy.

Don

10th Jul 2018 21:22 UTCDana Morong

The issue of wires comes up every so often. This situation is actually easily dealt with by those who are willing to think and to consider what works well for each test. It is not necessary to use platinum wire for all tests requiring wire, nor it is necessary (nor desirable) to use nichrome or iron wire for them all. Each works well for certain types of tests. For flame tests, iron wire or nichrome wire work well because platinum wire, so often saturated with sodium compounds (such as borax and microcosmic salt) will give the pervasive sodium flame. And iron and nichrome do not work well for bead tests as their metals can give their colors to beads (it should be obvious that the chromium in nichrome can give a color to beads – but nichrome is better used with flame tests). So flame tests, when done on wire, are best done on nichrome or iron wire, which has the added benefit of being so cheap that an end may be clipped off after use and thrown away.

Platinum wire should be reserved for bead tests of borax and microcosmic salt (the latter more commonly known as ‘salt of phosphorus’). Generally soda beads are performed on charcoal. The reason why platinum is so useful for the borax and the microcosmic salt (or S. of Ph.) beads is that it is a catalyst, which makes the reactions go much quicker and smoother. Also, platinum does not add color to these beads. However, as platinum is so sensitive to various volatile semi-metals (particularly arsenic, then antimony, bismuth, and some other in descending order), it is best, whenever one suspects that there may be any of such in the sample, to use the tube test first (tube tests work particularly well for volatile semi-metals), to determine whether there is any of the damaging semi-metal in the sample. Furthermore, sulfur isn’t so great for the platinum, so it is best to first roast off the sulfur, converting it into oxides, before the bead tests (if one used the tube test, that would show up sulfur as well). Then, if there isn’t any platinum-destroying stuff, one may then use platinum wire (which works best on the oxides of metals). If there is the semi-metal (shown up in the tube test), then one may use other means, such as a raw bead (perhaps first built up on the wire, then placed on a charcoal block, and then the assay added to it, so that it does not get with the platinum) on a support such as charcoal block, or possible a graphite rod, such as pencil lead sticking out of a drafting pencil. Such devices work, although not as well as platinum wire, but their advantage is that their use obviates the hazard to the platinum of its fusing with arsenic (or other volatiles) and getting brittle and the end of wire breaking off, making it shorter.

I have used pencil lead (held by a drafting pencil) for bead tests, and found it works better when sharpened. Of course, it doesn't work as well as platinum, but if there is traces of arsenic or antimony, it is preferable, then one can snap the end off and re-sharpen it. I also found that the harder types (H3 and H4) worked better than H2, possibly because of the clay mixed in with the graphite (to make it harder).

The most need of all, however, is time, wits, and experience. One cannot get much done when one does not fully understand what is going on, and it also takes time to be able to learn something new. Experience comes from actually doing the tests first on known materials, and seeing how they come out (then, afterwards, one may run a known test against an unknown to compare). It also requires doing such tests more than once, as results may vary. Only with experience can one really benefit from such tests (bead colors in books may vary due to color tint errors and variations in publishing then, but actually making beads with known materials can be very educational). If one truly wants to learn how to test minerals, one has to be willing to take the time and effort to learn this, and to gain experience, so as to be able to make wise choices.

11th Jul 2018 15:53 UTCDonald B Peck Expert

Great post, Dana.

An added note: It is worth while to make a collection of powdered minerals that can be used for comparison in any kind of test (flame, bead, wet chemical, etc). The "discard" stuff from collecting and trimming works fine, it just needs to be free of other minerals. Store in small labeled pill vials.

12th Jul 2018 09:38 UTCAlysson Rowan Expert

I still use microcosmic salt on occasion, as well as borax and sodium carbonate. I thought that I might be the last!

one of the important things to remember is to roast your mineral before using a platinum wire - whuich volatilises any arsenic

16th Jul 2018 23:54 UTCRocky Mineralowicz

Thanks for the advice on roasting samples before using with a Pt wire. I already have had a small piece of my wire get brittle and break off. I don't want that to happen too often.

Thanks also for the suggestion as to wire alternatives.

You can search ebay for microcosmic salt and find a guy selling some which is where I got mine. Cost is under $12 including shipping which is probably a similar price as the Bakewell Cream. It is probably purer but you get a lot less.

17th Jul 2018 01:13 UTCDana Morong

Sometimes it is best, if the sample has lots of arsenic (or antimony) to use graphite rod instead, as it is hard to roast out all the arsenic, and just a bit can make the used end of Pt wire brittle and break off. Years ago, I had the wire break off when I was trying to test some raw metals - raw metals can, with heat, make the wire brittle (I just Had to experiment, didn't I? But I did learn from it). Best to stick with the oxides for the bead tests. Fortunately I learned before I ran out of Pt wire (I got some more, and had to put it into the glass holder), but as it is now hard to get, and costly (once, years ago, I bought a 2-inch length of 26-gauge Pt wire for $5, a bargain at the time - it may be more by now), it is best to be careful with it.

17th Feb 2023 09:33 UTCAlf Olav Larsen

Mineral friends,

Does anyone out there know where in Europe I can buy microcosmic salt?

Alf Olav

17th Feb 2023 11:01 UTCChristian Klein

search for "Natriumammoniumhydrogenphosphat" or similar names in other languages.

Problem may be that most dealers will not sell to private folks. Talk to a chemistry teacher, perhaps you can get some there. Anyhow, you will not need much.

maybe these guys sell to end users:

https://klueverundschulz.de/1012/Natriumammoniumhydrogenphosphat-x-4-H2O-98-reinst-Phosphor-Salz

concerning Pt wire and alternatives: sticks made from MgO (magnesia) are just great.

https://klueverundschulz.de/magnesiastaebchen.html?number=1327100

make a pearl, break off the end with the pearl to keep it, and have a fresh end for the next pearl.

so long

Christian

22nd Mar 2023 16:04 UTCAlf Olav Larsen

When you can't buy it, make it. A successful synthesis of microcosmic salt.

Alf Olav

23rd Mar 2023 16:05 UTCSteve Hardinger 🌟 Expert

Please post a recipe (or reference to same) for this material.

23rd Mar 2023 19:41 UTCAlf Olav Larsen

The recipe is given in the following youtube film. However, I increased the chemicals by a factor of ten.

23rd Mar 2023 06:13 UTCAlan L. Melbourne

The crystal growing sets from toy shops are usually sodium hydrogen phosphate (rarely alum these days because that produces less extensive growths). I got some from my grandson when he was finished growing his and tired of it.

If you get hold of any old incandescent light bulbs, break them carefully and collect the little metal holders of the tungsten filament. They are (or should be) molybdenum and serve quite well for bead tests when mounted in glass, but can't take as much heat as platinum. Worth a try.

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