Cyrus - 27-7-2005 at 17:06
I tried to synthesise some graphite bisulfate yesterday.(approximately C24HSO4) following the procedure outlined in O. C. Braur's book of
inorganic chemistry.
1 gram of graphite powder was suspended in 10 ml of conc. H2SO4. (from draincleaner, apparently 98% conc.) 0.150 g of K2Cr2O7 was dissolved in approx.
4 ml of conc. H2SO4. Braur called for 3 meq. of "active oxygen" for the carbon, and supposedly this means that one needs 0.1 g of Cr2O3
dissolved in H2SO4 for 1 g of graphite. I have never heard of the insidious meq. before, but I'm guessing it stands for molar equivalents.
Anyhow, I remembered reading on this site that Cr2O3 takes forever to dissolve in H2SO4, so I decided to use K2Cr2O7, and guessed that the active
oxgen consisted of the 2 "Cr2O3"s found in the dichromate ion. Rough reasoning, I know. Doing a bit of calculations, I decided that 0.147
g of K2Cr2O7 were necessary to oxidize my one gram of graphite, and rounded that up to 0.15g. 
When the suspension of graphite and the dichromate/sulfuric acid are mixed, one is supposed to wait 15 minutes, by which time the graphite powder is
supposed to greatly expand and form a dark blue color. After 5 minutes of mixing them, small bubbles formed, and continued to form about 20 more
minutes. Nothing else happened, so I figured that my assumptions about meqs were wrong and that 0.2g more K2Cr2O7 might help. Nothing happened when
it was added. No color changes were noted (except at 23 minutes I pointed a bright light right at the test tube, and could barely percieve a
turquoise/blue color... or was that the chrome compounds... or the test tube... or my eyes @ 10:30 pm?)
The "products" were then filtered through glass wool and the filtrate dripped into some water; while the dichromate/ sulfuric acid was
yellow/brown at the beginning, the filtrate was dark forest green. What's left on top of the glass wool looks like plain graphite to me.
I'm currently washing it with H2SO4. (graphite bisulfate apparently decomposes in water.)
I'm fairly sure that this reaction failed. Probably I misunderstood meqs, and my sulfuric acid may have had some water in it somehow (after all,
it is just drain cleaner) which could have decomposed the graphite bisulfate as it formed. Has anyone else attempted this synthesis?
The synthesis of aluminum chloride graphite looks daunting, but supposedly bright blue lustrous crystals are formed. I love beautiful chemicals...
edit- I changed all of my incorrect instances of "CrO3" to "Cr2O3".
[Edited on 29-7-2005 by Cyrus]
chromium - 28-7-2005 at 00:52
I have not done this synth but H2SO4 + K2Cr2O7 is commonly used oxidising mixture that oxidises almost anything organic. Green insoluble Cr2O3 is one
of products. If your sulfuric acid contained anything organic ( and i am sure, it contained ) then you just used your K2Cr2O7 to oxidise it.
I belive that to make something so unstable as graphite sulfate you need especially pure reagents.
[Edited on 28-7-2005 by chromium]
vulture - 28-7-2005 at 09:41
Nitrate and chlorate treated graphite is said to be viciously explosive. No specific data though.
Cyrus - 28-7-2005 at 15:40
Yes, the filtrate was green like Cr2O3. The graphite was supposedly >99.6% pure, but I got it off ebay, so who knows? 
If the impurities in the sulfuric acid were the cause of the Cr2O3, then when I mixed the K2Cr2O7 and the sulfuric acid, that should have formed a
green color, but it didn't... I'm guessing that the graphite was at least partially oxidized. Perhaps I'll retreat it with, oh, 5x as
much K2Cr2O7 as "needed".
Edit- Tim, you're right. That's not the first time I've substituted "CrO3" for "Cr2O3". 
[Edited on 29-7-2005 by Cyrus]
12AX7 - 28-7-2005 at 20:21
CrO3?? Do you mean Cr2O3? CrO3 and salts are shades of red and yellow, IIRC (besides perchromate of course).
Tim