Chemistry of inorganic compounds – Oxygen or compound thereof – Metal containing
Patent
1985-10-16
1988-07-26
Stoll, Robert L.
Chemistry of inorganic compounds
Oxygen or compound thereof
Metal containing
C01G 3714
Patent
active
047599227
ABSTRACT:
A new anhydrous sodium dichromate in flakes, Na.sub.2 Cr.sub.2 O.sub.7, m.p. 356.degree. C. (dec. 400.degree. C.) is described, characterized in that it comes in flakes with an area of approx. 1 cm.sup.2, thickness 0.5 mm and apparent specific gravity 1.10 (absolute 2.748) at 25.degree. C.; it is not deliquescent, nor does it become powdery. It is prepared from dihydrate sodium dichromate or aqueous solutions thereof using a new process in two stages, namely (a) evaporation-melting of the dihydrate salt or concentrated aqueous solution at a strictly controlled temperature of around 380.degree. C. and no higher, and (b) flaking of the melted mass obtained thereby, as it is being rapidly cooled to 150.degree.-160.degree. C. The apparatus for carrying out the process is also claimed; said apparatus consisting essentially of a dehydrator-melter oven, a flaker rotating at 10-20 revs per minute and a heat recovery system. The thermic contribution, respectively positive and negative in the two stages, is provided by means of a particular eutectic mixture of melted salts, which melts at 139.degree. C. Said mixture is composed of KNO.sub.3 52.2%, NaNO.sub.3 7.0%, NaNO.sub.2 39.4%, K.sub.2 Cr.sub.2 O.sub.7 1.4%.
REFERENCES:
patent: 4171248 (1979-10-01), Carlin
Sorokin et al, "Chemical Abstracts", vol. 72, 1970, #134789j.
Karnaev et al, "Chemical Abstracts", vol. 83, 1975, #199500e.
Luigi Stoppani S.p.A.
Stoll Robert L.
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