With my recent interest in sulfur chemistry I, of course, cannot leave out the almighty SO
3, or oleum for that matter.
I want to personally thank Vitus_Verdegast for posting this most informative piece of chemistry:
Post 463311
(Vitus_Verdegast: "More suggestions...", Chemistry Discourse).
Na2S2O7 + 2 H2SO4 __> H2S2O7 + 2 NaHSO4
H2S2O7 <___> H2SO4 + SO3
Apparently the only thing you need to get a good strength oleum, and thus SO
3, is Na
2S
2O
7. Many hive members have expressed 'difficulties' in preparing it by the traditional way of heating sodium bisulfate.
To my knowledge thermal decomposition of persulfates has only been briefly mentioned here :
Post 480352
(Chewbacca: "decomp products", Chemicals & Equipment). However, it seems to be the preferred method to get highly pure disulfates in a controllable way and high yield. I think the first report of that method can be found in
Chem. - Ztg., 45.1921;1113-1114, which was a pain in the ass to get from the library and finally the wrong publisher and volume (always fun to get stuff from pre-WWII).
On the other hand the few sentences from
Inorg.Chem., 21.1982;744 and
Ber.d.D.Chem.Ges.B, 71.1938;2596 (in that order) seem to be enough to explain how it is done :
"
Pure K2S2O7 was made by the thermal dissociation of analytical grade K2S2O8 from Merck at 290°C for 1/2 h in a stream on N
2 to avoid contamination with H
2O.
Sulfur trioxide was not given off. "
"K
2S
2O
8, when heated to 290°C for half an hour gives off exactly 1 atom of oxygen"
I think the process for preparing anhydrides from pyrosulfates (
Post 462958
(Rhodium: "Na-Acetate + Na-Pyrosulfate -> Acetic Anhydride", Novel Discourse)) should be retried with pyrosulfates prepared this way.
According to
Post 246368
(Antoncho: "Re: Nitroalkane Preparation FAQ", Methods Discourse) oleum can be produced by bubbling sulfur trioxide into sulfuric acid.
Now for the questions that won't let me sleep:
Does sulfuric acid / low % oleum readily take up SO3 ?? How does temperature influence the uptake ?
Who around here makes their own oleum / SO3 - and how ?
prior art overviewA must read :
Post 418829 (missing)
(lugh: "Industry", Chemicals & Equipment)1) SO3Post 58152 (missing)
(terbium: "SO3 from P2O5", Chemistry Discourse) - a bit counter productive
Post 259376
(lugh: "Re: Methylene Sulfate", Novel Discourse) - decomposition of ferrous sulphate
decomposition of various disulfates
CA, 1960;20435 : Li
2S
2O
7 decomposes at 60 - 70°C (!)
Bull.Soc.Chim.Fr., 1972;4106-4110 K
2S
2O
7 at 440°C
Rev.Chim.Miner., 4.1967;589-620 : BaS
2O
7 at 160 - 300°C
Anal.Chim.Acta, 20.1959;20-25 Na
2S
2O
7 at 197 - 800°C
Acta Chem.Scand., 1.1947;781-789 2) pyrosulfates from bisulfatesCA, 1954;5009. J.Prakt.Chem., 5.1872;367Patent BP904971
3) pyrosulfates from sulfatesPatent DE40696
Liebigs Ann.Chem., 172.1874;106J.Chem.Soc., 27.1874;212--
psyloxy--