Hales’s apparatus

Figure 4.2 Hales s apparatus for the collection of the gas expelled from a substance by the action of heat...

In a memoir on spathic iron ore (ferrous carbonate) read in June 1774, Bayen showed that the mineral on heating or dissolving in acids lost what the English call fixed air . He used Hales s apparatus, measuring the elastic fluid or gas (gaz) evolved, which he found was absorbed by fixed alkali (potassium carbonate) to form a crystalline salt (potassium bicarbonate). He concluded that the mineral is a compound of i part of fixed air or gas and 3 parts of metallic iron, but it is really a compound of i part of fixed air and i -6 of ferrous oxide. 

Fig. 10. Hales s Apparatus for Measuring the Volume of Gas evolved BY Heating a Substance in a Retort.

Guerlac could not determine if Lavoisier read the Vegetable Staticks before 1772, but argued that Lavoisier should have been familiar with Hales s experiments reproduced in Rouelle s lectures Guerlac, Continental Reputation of Stephen Hales, 25-35. On Lavoisier s apparatus, see F. L. Holmes, Lavoisier the Experimentalist, Bulletin for the History of Chemistry 5, 1989, 24-31 idem, The Evolution of Lavoisier s Chemical Apparatus. ... 

Hales s ventilators were double bellows worked manually or by a windmill. Similar apparatus was simultaneously devised by Triewald in Sweden, which was fitted to ships in the spring of 1741, and Samuel Sutton devised a much more practical apparatus depending on the rise of heated air, fresh air taking its place, which was brought to the notice of the Royal Society by Dr. Mead, a model being shown. Both Hales and Sutton had great difficulty in getting their ideas tried on ships. Sutton complained, justly, that Hales had seen the experiment with his apparatus and heard Dr. Mead s account of it, whidi account was published in the Philosophical Transactions some time before the book of Ventilators was printed. Hales does not mention Sutton in his... 

The apparatus (Fig. 36) was very elaborate and only part of it is reproduced here. The iron retort was heated in a furnace and was connected by a luted joint with a wide tube passing through the wall of a wood or metal trough filled with water. This tube ended in a sphere, from which a vertical tube passed inside a tall bell-jar filled with water, the surface of which was covered with oil. Lavoisier says this apparatus is adapted from Hales s by Rouelle, with some changes and additions made by himself (he could have seen it in Rouelle s lectures). 

At the beginning of the 18th century S. Hales, an English scientist, invented a pneumatic bath. In this apparatus the vessel where a gas was formed (a retort with a reaction mixture) was separated from the collector for the liberated gas. The collector was a flask which was turned upside down and filled with water. Penetrating into the flask, the gas bubbles displaced water and the flask became filled with the gas under study. 

Sir John Pringle, Six Discourses delivered by Sir John Pringle, Bart, when President of the Royal Society on occasion of Six Annual Assignments of Sir Godfrey Copley s Medal. To which is prefixed the Life of the Author. By Andrew Kippis, D.D. F.R.S, and S.A. London, 1783 i f. A Discourse on the Different Kinds of Air, delivered Nov. 30, 1773 summary in Ohs. Phys., 1774, iii, 161 Fourcroy, (2), iii, 387 (ib., 389-414 on apparatus used from Hales to Lavoisier) Gmelin, (i), ii, 730-9. 

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