Calx of mercury

Since the carbon disappears completely in the revivi-cation of the calx of mercury, and we obtain nothing but fixed air and mercury, we are forced to conclude that the principle to which up to now has been given the name fixed air is the result of the combination of the eminently respirable portion of the air with the carbon. ... 

The strange calx of mercury played a crucial role to change this state of affairs.It had long been known to chemists for the peculiar property of being reduced to mercury without charcoal, thus by implication... 

The French scientist Antoine Lavoisier (1743-1794) was one of the first to use an analytical balance like the one shown in Figure 3-10 to monitor chemical reactions. He studied the thermal decomposition of mercury(II) oxide, known then as calx of mercury. Mercury(II) oxide is a powdery red solid. When it is heated, the red solid reacts to form silvery liquid mercury and colorless oxygen gas as shown in Figure 3-11 on the next page. The color change and production of a gas are indicators of a... 

The first day of August in the year 1774 is one of the most memorable dates in the history of science, and, indeed (although unknown to most historians), in the history of civilisation. On that sunny day, at Bowood near Caine in Wiltshire, where Priestley held the post of librarian and literary companion to Lord Shelburne, he focused his new glass upon some red calx of mercury, or mmurius calcinatus... 

Gloss (column 28—fused form of any substance— C connotes calx, so that the first symbol below the header is calx of mercury). 

History records that in October of 1774 Priestly visited Paris. There he met Lavoisier, to whom he described his latest discovery—the new air in which the flame of a candle burned much more brilliantly than in common air. He also told Lavoisier how he obtained it by heating the calx of mercury or the calx of lead.2 ... 

Figure 5.4 The apparatus used by Lavoisier to form the calx of mercury by heating the metal in air...

He admitted that Lavoisier s experiments proved that pure air or dephlogisti-cated air (oxygen) is fixed in combustions and in calcination of metals, but he supposed also that phlogiston, which is the matter of light, is at the same time emitted. The reason why calx of mercury (red precipitate) is reduced at a red heat without the addition of phlogistic material such as charcoal is that phlogiston is ... 

Priestley concluded that phlogiston is present in a combined state in metals, just as fixed air is present in chalk, both being expelled again by acids. He repeated the experiment with calx of mercury, the inflammable air being confined over mercury, and observed that even though the inflammable air was previously well dried with fixed ammoniac [calcium chloride], water was formed in sufiicient quantity . He thought this water was contained in the gas and is deposited when this kind of air is decomposed . Priestley was very undecided whether the water was contained in the calx or in the inflammable air or both, but the section is headed Experiments which prove that Water is a necessary ingredient in inflammable air . 

The theoretical interpretation of this experiment was a tricky business. Priestley later recognized that the red calx of mercury upon heating actually emitted... 

Jorgensen, 1909, 140, 145, says it is really curious that a whole series of publications like Bayen s on calx of mercury should have completely escaped Priestley s attention, yet this seems actually to have been the case Cuvier s suggestion, 1828, 65, that Bayen s papers in 1774 avait donn6 k Priestley I idee. . . de decouvrir I air pur , is most improbable the discovery was made by accident (see p. 256). 

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