DIFFICULTY OF OUrAlNlNG ALUMINE. |4l 



xxr. 



On, the Difficulty of obtaining Alumine in a State of Purity . 

 ByK.T. 



To Mr. NICHOLSON. 

 SIR, 



A OUR Journal being open lo every difquifition which may 

 contribule to the progrefs of fcience, it may not be deemed 

 impertinent to a(k you, or fome of your correfpondents, to 

 point out the bed method of" preparing pure alumine. 



You may, probably, refer me to our modern authors on A'umlneob- 

 chemiftry, but I aver that the methods therein recommended ing faturatedV- 

 do not anfwer the purpofe. For if a fat u rated folution of lutions of alum 

 alum of commerce, be decompofed by a like faturated folution *" *«'''ah, 

 of a carbonated alkali, the alumine obtained is harfli to the 

 touch, rather fpungy, and llrongly adheres to the tongue. 



This earth, although wafhed as often as you pleafe, always appears to con- 

 reddens the blue juice of the flowers of mallow, as well as f^j^L^u' * ** 

 of other delicate vegetable blues. It may be wholly dif- 

 folved in about !00 parts of boiling water: and the folution 

 becomes very turbid by muriate of barytes. 



If, on the other hand, a dilute folution of alum be decom- D''ute fdutions 

 pofed by another of alkali, a quite different produd will be ^^"[^g^'^^J'^^^5 

 obtained. The alumine produced, on being deficcated js not ance, 

 porous, but fplils into pieces like ftarch ; and has, before it is 

 nearly dry, a certain degree of tranfparency ; it breaks with 

 a fmooth and nearly conchoidal fra6fure ; it does not adhere to 

 the tongue like the former, and has no eartliy appearance. 

 This, like the former, cannot be freed from the adhering acid, 'i^ewife add. 

 It alfo changes fine vegetable blues to red, although ever 

 fo much waflied. What is the reafon of this ? Is there no 

 method of forcing this earth from the adhering acid? or is it 

 perhaps a characteriftic of the earth itfelf, to redden vegetable 

 blues. If you will pleafe to anfwer this quefiion, or point 

 out a better method for procuring this earth pure^ you will 

 much oblige, 

 Camdeii'Toivrif Sir, Your conflant reader, 



May2S, 1804. R. T. 



REPLY. 

 THIS letter having arrived fo late in the month, I can only 

 for the prefent olTer it to my other ccrrefpondents. 



SC/ENTIfJC 



