250 ALKALIES. 



moist hands, as it immediately blazes, and we have in that case, both 

 the actual and potential cautery. 



(i.) Hydrogen gas, heated in contact with potassium, dissolves it, 

 and becomes spontaneously inflammable, but loses this property by 

 standing, and deposits potassium again. A solid compound of potas- 

 sium and hydrogen, is formed by heating the gas and metal together, 

 with a spirit lamp. It is gray, dull, infusible, and not inflammable, 

 except at a high heat, when it burns vividly. 



7. POWERS OF COMBINATION. 



They are almost universal, as will appear farther on ; it unites with 

 iodine, chlorine, the metals and most of the combustibles, &c. and it 

 decomposes the acids, most of the oxides and salts, and animal and 

 vegetable bodies, and few substances, simple or compound, are un- 

 affected by it. Its greatest prerogative however is to attract oxygen, 

 which it takes from every thing, even from glass and stones, and 

 from the firmest compounds, both natural and artificial. 



8. In relation to the state of our knoivledge, it is an element. The 

 most singular circumstance in the character of potassium is its levity : 

 it resembles the metals very much in the greater number of its prop- 

 erties, but differs from them remarkably in specific gravity, while in 

 its extreme inflammability it is assimilated to the most combustible 

 bodies.* 



9. POLARITY AND COMBINING PROPORTION. 



Like other inflammable and metallic bodies, it resorts to the nega- 

 tive pole in the galvanic circuit, and is therefore electro-positive. Its 

 combining number or chemical equivalent has already been stated to 

 be 40, hydrogen being l.f 



10. USES. As yet they are exclusively philosophical. In the 

 hands of the chemist, it is a fine instrument of analysis, especially in 

 the agencies which it exerts upon oxygen. It is a splendid substance 

 for experiment, admitting of many beautiful and instructive modes of 

 exhibition. From the improved modes of obtaining it which have 

 been discovered, there seems little reason to doubt that it may be 

 manufactured to any extent that may be required, and its introduction 

 as a new means of annoyance and destruction, would perhaps not be 

 improbable, were it not that it might prove nearly equally dangerous 

 to friend and foe. 



* These properties, with the remarkable fact, that during the galvanic decomposi- 

 tion of the alkali, although oxygen is evolved at the positive pole there is no hydrogen 

 given off at the negative, led to the presumption that potassa is not a compound of 

 oxygen and potassium, but of potash and hydrogen; the oxygen arising from the 

 decomposition of water, and the hydrogen of that fluid going into union with the 

 alkali to produce potassium. For an ingenious discussion of these and some other 

 similar views, see Murray, 6th ed. Vol. II, p. 27. 



t Mr. Murray has stated some reasons why it may rather be supposed to be 41, 

 see as above. 



