Jl Kew and Curious variety of C ambus tion>. 387 



The colour thus prepared, possesses a bluish shade; but 

 the arts often call for a deeper shade, somewhat yellowish, 

 but of the same beauty and elegance. To efFectthis change 

 it is only necessary to dissolve a pound of common potash, 

 in a sufficient quantity of water, and add to it ten pounds 

 of the colour prepared as above, and warm the whole over a 

 moderate fire. The mass soon deepens and acquires the 

 requisite shade. If too long boiled, the colour approaches 

 to Scheele's green, but always surpasses it in beauty and 

 splendour. The alcaline fluid which remains may be used 

 in the preparation of Scheele's green. 



23. A mineral spring which issues from an Argilo-cal- 

 eareous soil, near Sales, in Piedmont, Italy, has been found 

 to contain Iodine. Its spec. grav. is 1.0502. It has a 

 strong urinous odour, and a briny, pungent taste. Bubbles 

 of air are constantly disengaged from it. Volta in 1788 

 found it to contain mur. of soda, and Romano in 1820, dis- 

 covered in it, various earthy muriates, and a little oxide of 

 iron. At length Angelini, an Apothecary at Voghera, by • 

 employing starch as a reagent, obtained the blue colour 

 which indicates Iodine, and he succeeded in presence of Dr. 

 Ricotti and Luc. Barenghi, in extracting a certain quantity 

 of this substance by'the process which is followed in procur- 

 ing it from the mother waters of salt petre. 



It is remarkable that for a long time, the mineral waters 

 of Sales have been successfolly employed in scrophulous 

 affections, and especially in the dispersion of Goitres. 



24. — .JJ new and curious variety of combustion. — Doberei- 

 ner, professor at the university of Jenaa, has discovered 

 that Platina, in a spongiform state, occasions, at common 

 temperatures, the combination of oxygen and hydrogen, and 

 that so much heat is developed from its action as to render 

 the metal incandescent. 



This singular and interesting result has been confirmed 

 by Dulong and Thenard, who have varied and extended the 

 experiment, with a view to discover the theory, but in.lhis 

 they have not succeeded to their own satisfaction. They 

 find that platina sponge becomes incandescent when it is 

 placed in a stream of hydrogen gas, at the distance from the 

 orifice in which it mingles with the atmospheric air. In 



