Experiments for obtaining and presc7'mng Potassium. 209 



tube became choked again, and having become impermeable to the 

 iron rod ; the grate was thrown down and the retort cooled. I was 

 disappointed however on removing the receiver in finding little potas- 

 sium in it, nearly all being condensed in the tube of the retort which 

 had been kept cool by means of wet cloths. It immediately occurred 

 to me that the circumstance of cooling the tube had prevented the va- 

 por of the metal from passing into the receiver ; accordingly I de- 

 termined to obviate this supposed effect in the next experiment by 

 letting the tube heat as much as it would, thinking by this means the 

 metal would be condensed in the receiver. The second experiment 

 was conducted in every respect like the first, except the circumstance 

 of cooling the tube ; and the result would I presume have been sim- 

 ilar had not the retort been fused in the midst of the operation. 

 This accident is the less surprising, as few bottles of the kind are 

 thick enough to stand more than two operations. 



The potassium obtained in the two operations was by no means 

 the pure metal, but an alloy of carbon, potassium, and I think iron, 

 though Berzelius states it to be carbon and potassium with potassa ; 

 that it contains iron I am sure from having obtained its oxide by de- 

 composing the alloy in water ; but whether chemically combined or 

 not I am unable to determine. The alloy is not uniform in appear- 

 ance, or in other properties. Some portions of it appear of a lead 

 color, soft and malleable ; others hard, brittle and of a grayish as- 

 pect, nearly resembling cast iron in its fresh fracture. This variety 

 has the property of exploding with violence when suddenly struck 

 with a hammer or rubbed briskly by means of an iron rod. There is 

 a third variety which is the black powder; this, though it contains po- 

 tassium, has less than either of the two other varieties ; yet it will give 

 the rose colored flame when thrown into water. 



. The alloy is detached from the tube, by first pouring in naphtha to 

 protect it from the air ; then by hammering the tube, the greatest part of 

 the alloy is separated ; the rest may be detached by means of an iron 

 scraper, but much caution is necessary in using the scraper, lest the 

 friction cause the compound to explode in the tube, as once occurred 

 to me before I had learnt its detonating property. These accidents 

 are completely prevented by keeping the alloy covered with naphtha. 

 The product, when separated from the tube, ought to be distilled as 

 soon as convenient, for much of it is oxidated by keeping it in that 

 state for any length of time. Acertaining from the second experi- 

 ment as well as from the first, that only a minute portion of the me- 



