A L K

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j

A I K

crystallized. The crystallized texture was stillmore decided with three portions of potassium.These amalgams will take place without heatwhen the potassium is free from oil or oxyd oilits surface and quite clean. They often occuraccidentally by the fall of particles of potassiumon the mercury bath, which, as soon as theytouch the mercury,, move about on its surfacewith great rapidity, and soon disappear by beingabsorbed by the fluid metal. Much heat isgiven out when potassium and mercury unite.

Potassium 2 measures, arsenic 6 measures..This alloy is easily made and much light isgiven out at the time, but instead of having a'metallic lustre it is of a dull chesnut brownhue, and when in contact with water it givesout a much smaller hulk of hydrogen gas thanthe same quantity of potassium gives when al-loyed with any other metal. This gas wastherefore examined with more care. A bentglass tube was filled with azote over mercuryand 2 measures of potassium, and a piece ofarsenic were introduded into the tube and unitedby fusion- The azotic gas was not in any de-gree altered. Water was then thrown up whichcaused a brisk effervescence and the productionof potash, and the alloy was entirely destroyed,leaving only a light fiocculent. matter like ker-mes. The water was boiled to compleat thedecomposition of the arsenical alloy. The onlygas produced was 82 measures of arsenicated'hydrogen. This experiment was repeated manytimes with different proportions of potassium,the gas being always measured, and it wasfound to be pretty accurately in direct propor-tion to the quantity of potassium used : but itwas also found that the same quantity of po-tassium which when unalloyed with arsenicgave 79 parts of pure hydrogen, would giveonly on the average 33.36 parts of ’arsenicatedhydrogen. This led to the analysis of arseni-cated hydrogen. This gas was prepared bothby moistening the alloy of arsenic and potas-sium, and by adding muriatic acid to an alloyof 3 parts of tin and 1 of arsenic. A givenquantity of this gas was confined in a glassvessel over mercury, in contact with a vesselcontaining tin which was kept in fusion for threequarters of an hour. This process extracted 1all the arsenic from the gas, which then re-turned to the state'of simple hydrogen, as wasdetermined by there being not the least depo-sition of arsenic on the sides of the vessel inwhich the gas was subsequently burned. Fromthe tesu.lt of several experiments which agreed

4 Phil. Trans, for

sufficiently well, it was 1 shewn that 100'mea-sures of arsenicated hydrogen expand to 140parts after the extraction of the arsenic. 13ucthis circumstance would only account for partof the apparent deficiency in the quantity ofgas produced by the action of water on the al-loy of arsenic and potassium, for if 110 mea-sures of pure hydrogen produce 100 measuresof arsenicated hydrogen', 79 of hydrogen (thequantity produced by each measure of pure:potassiumj should give 56.4 of the arsenicated.gas, whereas the quantity of the latter gas ac-tually produced, was only 33.36. This there-fore would imply some loss of hydrogen, orrather a condensation of it in some one or otherof the products so as to prevent it from as-suming a gasseous form, and- this- the authorswith great probability suppose to be the case inthe brown arsenical flocculi that remain after,the action of water upon the arsenical alloy,which fiocculent matter therefore will then he-a- Itydrurc.l of Arsenic .- The possibility of asolid compound of hydrogen and arsenic hasalso been inferred- by Sir H. Davy , as a resultof the following experiments on the action of”tellurium and'arsenic on potassium. d ’ Arsenic-being made the negative surface in a- powerfulgalvanic action taken in water, became darkcoloured and threw down a brown powder, atthe same time giving off. much inflammable -gas. Also an alloy-of arsenic and potassium-being heated in ammonia produced'a gas which-was principally azotey and hence the hydrogenof the decomposed ammonia must have enteredinto combination ■ with thearseniuret of-potas-sium.

Potassium heated in arsenicated hydrogen (toreturn to M. M. Gay Lussac and Thenard) be-comes immediately covered with a red crust,,dense fumes condense on the sides of the ves-sel, the gas is suddenly decomposed, and there-fore expanded, pure hydrogen appears, and thearsenic combines with the potassium into a;solid arseniuret similar to that produced by the-direct union-of arsenic and potassium.

Potassium may be readily alloyed with iron-by putting some iron turnings in the lower ex-tremity of the gun-barrel that projects beyond'the furnace (in the apparatus for obtaining po-tassium) instead of- leaving it empty to receivethe condensed potassium. In this case the iron-being long in contact with potassium in vapour-absorbs it, becomes flexible,' and often quite-soft, and is decomposable in air or water likeany of the other alloys of this substance. With—1810, p. 27, &.C,