290 



On Chemical Tests. 



[Oct. 



soluble in ammonia, insoluble in dilute nitric acid, and which blackens 

 in the sun, see 47, 106. 



b. Lead, by a white precipitate, which is not soluble in ammonia, but 

 which is soluble in nitric acid, see 69. 



c. Manganese, by the disengagement of chlorine gas. Melt soda, or 

 borax in a platina spoon, add a little manganese, or ore containing man= 

 gnnese, and a red colour will appear on keeping the spoon in the inte- 

 rior flame of a candle, but it gradually disappears; add nitre and place 

 the spoon in the exterior flame and the red colour again becomes visible, 

 which confirms the test, see 81 . 



(d) Ammonia, by dense white clouds, thus ; dip a rod in muriatic 

 acid, and if free ammonia be present, on holding the rod over the sub- 

 stance to be examined, dense white clouds of muriate of ammonia will 

 be seen to form, see 27, and 28. 



(e) Carbonic acid, by the effervescence produced on adding muriatic 

 acid to either a mineral, or a solution in which carbonic acid is present. 



(f) Pure muriatic acid is colourless, but it frequently contains iron 

 or chlorine which may be known by its being then of a yellow colour. 

 It may also contain sulphuric acid. Both the iron and the sulphuric 

 acid, may be detected by their proper tests, see 55 and 40. 



(g) The specific gravity of muriatic acid shoula be 1-170, but that of 

 commerce is generally from 1*156, to 1*160. 



12. ACID meconic. This acid yields a red colour with the persalts 

 ofiron,andan emerald green with the sulphate of copper. By these 

 tests the presence of opium may be discoverd 



(a) M. Couerbe gives the following table of the colours produced by 

 agitating the peculiar substances contained in opium with sulphuric acid 

 and air. The experiment is to be made in a four ounce vial with six 

 grains of the substance, and nearly half an ounce of sulphuric acid 

 mixed with a little nitric acid. Strong agitation is to be employed and 

 the colour is developed in a few minutes. 



Pure Sulphuric acid. 



Sulphuric acid mixed with a little 



nitric acid. 

 Thebaia. Instantly red, becoming 

 deeper. 



Narcotina- Yellow, turning red. 

 Codeia. Very pale green. 

 Morphia. Green, almost immedi- 

 ately. 



Meconin. In 21 hours superb rose 

 colour. 



Narceia. Mahogany colour. 



Thebaia. Rose colour, shade of 



yellow. 

 Narcotina. Blood red. 

 Codeia Green. 

 Morphia. Brown. 



Meconin. Turmeric yellow ; af- 

 terwards red. 

 Narceia. Chwcolate colour. 



