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How Do I Get 3 Mg Of Boron From Boric Acid?

 
 
Reply Thu 8 Dec, 2016 11:20 pm
Boric Acid has a density of 1.44. I am looking to obtain approximately 3 Mg of elemental Boron from Boric Acid purchased from a pharmacy. I have no small scale. However, I have a set of small spoons that range from 1/4 tsp down to 1/64 tsp. For volume, that is

1/64 tsp = 0.016 tsp = 0.07 ml
1/32 tsp = 0.032 tsp = 0.14 ml
1/16 tsp = 0.064 tsp = 0.28 ml
1/8 tsp = 0.125 tsp = 0.62 ml
1/4 tsp = 0.250 tsp = 1.23 ml
I have figured out that 0.42 tsp of Boric Acid =3 ml Boric Acid, (I think, Very Happy ).

However, elemental Boron is only a fraction of that Boric Acid.

How much Boric Acid do I have to use to get 3 Mg of elemental Boron, in teaspoons or ml?
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Type: Question • Score: 0 • Views: 381 • Replies: 7
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farmerman
 
  1  
Reply Fri 9 Dec, 2016 03:12 am
@Blickers,
its bucket chem, dont worry about the reaction. You will wind up (stoichiometrically) with about 1/2 the weight of Boron trioxide by just driving off the water Basically you are creating an anhydrous boric oxide which is kinda glassy. Finally, youll wind up with about 1/10 reaction weight of boron from the oxides.
If you need high purity in your final product, be aware of your lab ware (I guess Id use high qual glass ware , maybe a wide mouth beaker over a burner)

The real problem is the driving reaction of the boric oxide anhydrite. You can add about 1/2 the weight of the oxide glass in Mg powder to make a boric oxide "thermite".
This will leave you a mix of boron "grit" MAg Oxide, and Mag boride. You want to drive those off with some .1 N HCl.
THERE IS A CAUTION THT ENTERS HERE. YOU WILL be creating a bunch of Boranes (Hex, tri and DIBORANE).

Diborane is pyrophoric as it is driven off (It will explode in air as a function of the product weight being produced) . At low amounts its "cute" , youll be making blue pops of diborane going off. If you start going commercial -youd better have collection means or youll do a massive rearranging of your lab hood .(Do this in a hood and wear all the arm and eye protection)

If you know your chem and can see the product balance from my"back formulation", you can do the stoichiometry and equivalent weight calcs .
Just be careful at the borane production phase.

When you react the HCL to collect the boron (itll be grayish black chunks) put in some Sodium Bicarbonate (like 1 or 2 g) to keep from etching your glassware.

Are you using this for pottery? or reacting double bonds or are you collecting something radioactive??

Blickers
 
  1  
Reply Fri 9 Dec, 2016 11:23 pm
@farmerman,
Thank you for your swift and informative reply. Unfortunately, I misworded the question. What I should have written was, "What volume, (teaspoons or ml), of Boric Acid do I need to have 3 Mg of elemental Boron? I just figured out that by weight, Boron is about 17.4% of the total Boric Acid content. Boric Acid Molecular Weight =61.8, Boron Atomic Weight =10.8, so 10.8 / 61.8 = Boron is 17.4% of Boric Acid by weight.

So, if I'm figuring correctly, 1 tsp, (1.23 ml) of water = 1.23 mg of water).

Therefore, 1.23 ml of Boric Acid, (density 1.44 that of water), = 1.44 * 1.23 = 1.77 mg Boric Acid. Boric Acid is 17.4% of Boric Acid by weight, so 1 tsp Boric Acid yields 0.31 Mg of Boron. So it would take 9.7 tsps to contain 3 Mg Boron.

Have I got that right? It's after midnight, and my school days when I could figure anything more than 2 + 2 past midnight are way behind me. No pottery or radioactivity in the picture.
Blickers
 
  1  
Reply Sat 10 Dec, 2016 01:40 am
@Blickers,
Check that. Since 1/4 tsp =1.23 ml, not 1 tsp, it would take one fourth that amount, or 2.4 tsp or Boric Acid to contain 3 mg of Boron. Is that correct?
farmerman
 
  1  
Reply Sat 10 Dec, 2016 02:45 am
@Blickers,
Ive done a formula weight for you and H3BO3 contains 17.5% boron by weight. Assume the reactions are complete and your cleanup is efficient (DO NOT use aluminum or enamel- ware or any kind of ceramics for the reactions). Just solve for your needed 3mg by using a chart of equivalences from vol to wt.

There shouldnt be that much diborane released so youll probably just get a small pop.

Still, do it under a hood, lab safety
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layman
 
  1  
Reply Sat 10 Dec, 2016 02:50 am
I was told that boric acid was a good chemical for killing cockroaches. But, ****, I poured many pounds of it all over my crib, many times, and there are STILL about a million cockroaches over-runnin the joint.

What's up that, ya figure, eh, Farmer?
farmerman
 
  1  
Reply Sat 10 Dec, 2016 03:18 am
@Blickers,
theres 4 g of boric acid in a tsp. Thats 4000 mg (PS in order to even do the reaction you need to use boric acid powder).

Im not sure where your problem is(other than getting the weight to volume measurement correct.

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farmerman
 
  1  
Reply Sat 10 Dec, 2016 03:35 am
@layman,
wed eat palmetto bugs in Nigeria. Toasted up with garlic and cumin they werent that bad. (and I hate cumin)
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