CHEMISTRY. 



209 



the remaining chlorides into carbonates, the 

 carbonate of the new metal is with certain 

 precautions dissolved out with absolute alcohol. 

 The salt thus obtained being placed along with 

 mercury at the poles of a galvanic circuit, an 

 amalgam of caesium is the result : the avidity 

 of the new metal for oxygen is shown by the 

 fact that, while the familiar alkaline metals, 

 potassium and sidium, must when separated 

 be preserved in liquids which, like naphtha, con- 

 tain no oxygen, the separation in the metallic 

 state of cesium has not as yet even been effect- 

 ed : and in the condition of amalgam it oxi- 

 dizes in the air and decomposes cold water. 

 In entire accordance with such facts, ca?sium is 

 the most electro-positive element now known. 

 Symbol, Cs ; equivalent, 123.4. The hydrate 

 of protoxide of caesium, chemically the analogue 

 of hydrate of potash, is extremely caustic. Its 

 carbonate, bicarbonate, sulphate, nitrate, alum, 

 <kc.. have been investigated, and have in gen- 

 eral a close resemblance to the corresponding 

 compounds of potassium and sodium. The 

 quantity of ctesium in any source yet known is 

 extremely small ; but it is widely diffused in 

 nature. The largest proportion yet found in 

 any source is that given by Prof. C. D. Allen 

 (' Anier. Jour, of Science," Dec. 1862), as the 

 product from a lepidolite from Hebron, Me., of 

 which it formed somewhat more than 0.3 of 

 one per cent. It has been stated to be a con- 

 stituent of the human blood and tissues. The 

 chloride and perhaps other compounds of this 

 and the next named metal may, it is believed, 

 now be obtained in small quantities of dealers 

 in the rarer chemicals in this country. 



Rubidium. This second new alkaline metal 

 was discovered, in like manner with the former, 

 through spectrum observations ;. its character- 

 istic, two bands of dark red lying in the ex- 

 treme and usually invisible portion of the spe'c- 

 trum at the red extremity, having been detected 

 during prismatic analysis of the light colored by 

 an impure compound of caesium which contain- 

 ed it. The associated alkaline metals existing in 

 certain lepidolites being precipitated as above, 

 the precipitate is reduced with hydrogen, and the 

 chloride of the new metal being extracted with 

 water, is purified by repeated precipitation and 

 boiling. The chloride being con verted into a car- 

 bonate, caesium is removed by repeated extrac- 

 tion with alcohol ; and an amalgam of rubidium 

 is then obtained in the manner above described. 

 In this condition, rubidium also oxidizes in the 

 air and decomposes cold water : it is electro-posi- 

 tive in reference to potassium, but stands in the 

 scale below caesium. Symbol, Rb : equivalent, 

 85.36. Its hydrate is strongly caustic : several 

 of its salts have been investigated. Its chlo- 

 ride, like common salt, crystallizes (though not 

 readily) in cubes, which are permanent in the 

 air. Prof. Allen prefers the process of extrac- 

 tion of caesium and rubidium in the form of 

 bitartrates. The greatest quantity of rubidium 

 yet found is that obtained in 1862 by Bunsen 

 from a lepidolite from Rozena in Moravia, equal 

 VOL. II.-14 



to .03. Grandeau has recently found that ru- 

 bidium exists in the ashes of the beet, in to- 

 bacco, coffee, tea, and raw tartar, so that there 

 is little doubt of its presence in the human 

 system. Since it had previously been shown 

 to exist in many minerals, and mineral waters, 

 rubidium must be regarded as an element very 

 widely distributed in nature. An interesting 

 result of these discoveries, and of the determina- 

 tion also of the characters of oxide of lithium, 

 is that henceforth, instead of the familiar two, 

 we must admit at least fire positive fixed alka- 

 lies ; namely, cresia. rubidia, potassa, soda, and 

 lithia. The first three of these, also show a 

 remarkable tendency to exist associated, wheth- 

 er in the solid or liquid state ; and they mani- 

 fest a similarity of behavior that renders their 

 separation difficult. 



Thallium. This new metal, the existence 

 of which was suspected in 1860 by Mr. Wm. 

 Crookes, through detection by him of a before 

 unobserved green band in the spectrum of light 

 colored by certain residues probably containing 

 also sulphur, selenium and tellurium, was after- 

 ward chemically separated by him, and by M. 

 Lamy. of France the complete accounts of the 

 substance by both these explorers appearing in 

 1862. As obtained in quantity, thallium is a 

 metal strongly resembling lead, though in some 

 respects more similar to tin. Freshly obtained, 

 it is nearly as white as silver, and on cutting 

 shows a brilliant metallic lustre. It is extreme- 

 ly soft and malleable, easily cut and scratched 

 with the nail ; and like lead it readily marks 

 paper, but with a yellowish streak. Its density 

 is 11.9, a little higher than that of lead ; symbol, 

 probably Th ; equivalent not given. It fuses 

 at'290 3 C.=554F., and at a red heat volatilizes. 

 It tends strongly to crystallize, so that bars of 

 it obtained by melting crackle when bent like 

 those of tin. Its most remarkable physical 

 property is, perhaps, the green light which it 

 imparts to flames ; a quantity of the metal so 

 small as the ^.T^o.nTrs P arfc f a grain in a 

 flame is indicated in the spectrum by its char- 

 acteristic green band. The oxide of thallium 

 appears to have alkaline properties in a degree. 

 Several of the ordinary salts have been investi- 

 gated. Thallium is not a rare body, being found 

 in pyrites and associated with native sulphur, 

 from various localities. It can be reduced from 

 its salts by an electric current, or with char- 

 coal at high temperatures, or by precipitation 

 with zinc. For more full accounts of this 

 metal and its compounds, see " American Jour- 

 nal of Science," Sept. and Xov., 1862. 



LitTiium. The equivalent of this element 

 appears to be not yet decided. Troost has re- 

 cently found it 7.06 ; Diehl, 7.026 ; and Mallet 

 has given it as 7. Regnault, in calculations of 

 the specific and atomic heats of certain ele- 

 ments, has taken the equivalent of lithium 

 as t'i.43 (O being 8) ; but he repeats his sug- 

 gestion, long since made, that the true equiv- 

 alent is half this, the constitution and symbol 

 of lithia being according to his view L 3 O ; as 



