172 ESSAY XII. 



SECTION IX. 



That this metal is not incapable of attracting phlogiston, 

 appears from the blue colour which the sublimate receives 

 from the flame of a candle ; that it attracts it also via 

 humida, the blue colour likewise evinces (Sec. vn. (&)). (a) In 

 order to acquire more certainty on this point, the earth of 

 molybdsena was dissolved in boiling water, with the addition 

 of a little alkali. Into this solution were poured some drops 

 of muriatic acid, and it was divided into several parts ; into 

 each part there were put filings of different metals ; the 

 solutions soon acquired a bluish colour, which grew deeper 

 and deeper, and in an hour's time, during which the bottle 

 was now and then shaken, the colour became a very fine and 

 dark blue. That this colour depends upon phlogiston, may 

 be concluded from the following considerations: (1) If, 

 instead of the metals, you take the different calxes, no 

 change of colour takes place. (2) If there be dropped 

 into the blue solution a few drops of acid of nitre, and 

 the solution be then put into a warm place, the colour 

 disappears. It is therefore not a matter of surprise that 

 both silver and quicksilver should be attacked, since a 

 double attraction takes place, the muriatic acid uniting 

 with the metallic calx and the earth of molybdaena with 

 the phlogiston of the metals ; gold, however, is not attacked. 

 (&) If too much muriatic acid be added to the solution, it 

 acquires not a blue, but a yellowish colour, which at last 

 turns brown if the metallic mixture be digested. Here the 

 earth seems to attract more phlogiston ; for if this solution 

 be added to a solution of earth of molybdrena, the phlogiston 

 is more divided, and the mixture grows blue, (c) Lixivium 

 sanguinis, in which the acid prevails, precipitates this earth 



