Flotation- it's a lot older than you think!

In my posting of 10th April I commented on the fact that, although the 'invention' of flotation is often attributed to Francis Elmore in his patent of 1904, there was much interest prior to this, particularly in Australia, as there was a desperate need to develop a process which could be used to concentrate base metal ores, as gravity concentration was becoming impractical as the ores became leaner and more complex.

Amongst the comments on the posting was a very interesting one from Dr. Martin Rudolph, of the Helmholtz Institute Freiberg for Resource Technology, Germany, who  advised that the flotation process will in fact celebrate its 140th birthday on July 2nd this year!

It was on that day in 1877 when August and Adolph Bessel patented the first flotation process related to the beneficiation of graphite from a mine in south east Germany, which is still in operation today, currently operated by Graphit Kropfmühl GmbH, part of AMG Mining AG.

Martin has procured a copy of the 1877 patent and has kindly translated it into English:

Patent 1877 - No 42 – Class 22 Bessel Brothers (August Bessel and Adolph Bessel) in Dresden, Germany

Process for refining Graphite

Patented in the Deutsches Reich (German Reich) beginning July 2nd 1877

The crude impure graphite is mixed with a small quantity (1 - 10 pCt) of an organic substance which, when liquid, is not water-soluble or only slightly miscible, when solid, is neither dissolved in or wetted by water. These substances, as far as they can be practically used, are as follows:

1. All the fatty oils and rigid fats of the animal and plant kingdoms, and the fatty acids which can be obtained from them,
2. All etheric oils,
3. All the resins of the vegetable and mineral kingdom, their dissolutions, and the oils which can be obtained from them by dry distillation,
4. The rubber bodies, their dissolutions, and oils which can be obtained by dry distillation,
5. The so-called balsams of commerce,
6. Crude and refined petroleum, the by-products of refining, both the more volatile ones, such as ligroine, petroleum alcohol, and petroleum ether, as well as the less volatile, the so-called volcanic and engine oils,
7. Tar of brown coal, hard coal, wood, and peat, as well as the oily products of the distillation of these tars, as well as the residues remaining during their distillation,
8. Pitch of the trade,
9. Paraffin,
10. Gasoline,
11. Potato fusel alcohols,
12. Beeswax and vegetable waxes, as well as all oils obtained from those by dry distillation,
13. Shale oils and tar from sands,
14. Ozokerite,
15. Whale fat and whale oil,
16. Oils of bones obtained by dry distillation, as well as boiling out bones,
17. Cheese types of the trade,
18. Any mixtures and dissolutions of the bodies listed above.

The mixture of the graphite with the chosen body is made as intimate as possible so that all parts of the former come into contact with it. The mixture is then poured into water and the latter is heated until vigorous boiling. During this cooking the flakes of the graphite are observed to rise within the liquid while the earthy substances (clays) remain on the ground. The graphite floating on top is drained off and dried. If the graphite is simply boiled with water without prior mixing with any of the substances mentioned, such separation does not take place, nor is this done by desliming. The operation proceeds preferably with the flaky varieties of graphite.

 

Thanks for sharing this with us, Martin. We look forward to seeing you and your team in Cape Town in November for Flotation '17, and hopefully your translation might lead to some interesting ideas on 'new' reagents!