96 



ESSAY V. 



alkali, by a certain treatment with dried blood, vid siccd, or, 

 what is more convenient, with Berlin blue in the moist way, 

 may be almost completely neutralised. Phlogiston, it is 

 true, is generally assigned as the cause of this change ; but 

 in all probability the whole depends principally on an 

 animal acid. There appears at least, on the addition of 

 Berlin blue, an evident effervescence, and the solution may 

 be reduced to crystals. Alkali, thus changed and dissolved 

 in water, is generally called lixivium sanguinis, and pre- 

 cipitates all metals dissolved in acids; but does not pre- 

 cipitate in the least any of the earths, except as far as there 

 is any superfluous alkali present, which may be easily avoided 

 by adding some distilled vinegar. Now, if a quantity of 

 this alkali be added to a solution of manganese, a light 

 yellowish grey earth immediately precipitates, which is not 

 soluble in any of the mineral acids : both which circum- 

 stances happen only with metals, and thus clearly show the 

 nature of the precipitate. But what kind of metal it is 

 which manganese contains is not so easily ascertained. The 

 solution of cobalt does not lose its colour on adding sugar, or 

 any other phlogistic substance ; and zinc does not impart 

 any colour to acids ; these two substances consequently differ 

 from manganese, which does not, indeed, entirely agree with 

 any other of the known metallic earths. I have, however, 

 great reason to conjecture that it must be platina, the earth 

 of which is not yet known ; or a new metal, which at least 

 would agree with platina in the great difficulty with which 

 it fuses. To ascertain this, a series of experiments is begun, 

 which, if they shall confirm my conjecture, will make 

 manganese a still more remarkable substance. 



