1839.] 



On Chemical Tests. 



291 



b. Morphia and its salts, form a deep greenish blue solution with per= 

 muriate of iron ; and turn brown on adding a drop or two of iodic acid. 



The proper solvents of morphia are alcohol, and diluted acids. Ni- 

 tric acid turns it orange red, or if much acid is used, yellow, all the salts 

 of morphia aie intensely bitter, see /. » 



c. Narcotine is distinguished rather by negative than positive chemi- 

 cal properties. If pure it is not affected by permuriate of iron, nor 

 nitric acid. When morphia and narcotine are crystallized together in 

 an alcoholic solution, and when they are not quite pure, the narcotine 

 forms tufts of pearly thin tabular crystals, while the morphia is in short 

 thick adamantine prismatic crystals. 



d. Codeine differs from morphia and narcotine in being moderately 

 soluble in water and from this solution it may be obtained in large crys- 

 tals tending to the form of octahedrons. 



e. In cases of poisoning by tincture of opium, it is difficult to detect 

 it, if it has lain in the stomach a few hours. 



/. A minture of equal parts of strong aqua-ammonia, and alcohol will 

 produce in laudanum a crystalline precipitate of morphia in a few 

 hours. This precipitate of morphia may by being twice dissolved in 

 acetic acid, and twice precipitated by ammonia be obtained quite white. 



13. ACID nitric, detects (a) resin ; (b) starch ; (c) nitrogen j (d) 

 uric acid ; (e) iron from steel ; (f) tin ; (g) carbonic acid. 



a. Resin. When concentrated nitric acid is digested repeatedly 

 with gum, mucilage, gluten, jelly, extract, gum-resin, or other immedi- 

 ate vegetable product, it is partly converted into oxalic acid, but resin 

 is not. The resin results as a pale orange coloured mass, soluble in 

 water, but possessing no resinous properties, see 1 and 103. 



b. Starch. If a vegetable substance is digested for some days in 

 dilute nitric acid ; on the addition of alcohol, starch will be precipitated 

 if present, see 113 a. 



c. Nitrogen. This gas is set at liberty when animal matter is digest- 

 ed with nitric acid. 



d. Uric acid is detected in the analysis of urine by a pink or rose 

 colour on the addition of nitric acid. If a little of the solution contain- 

 ing the nitric acid be evaporated to dryness in a watch glass over a spirit 

 lamp, a beautiful purple colour is produced, which is improved by the 

 addition of water. 



e. Dilute nitric acid dropt on iron produces a grey spot, but on 

 steel, a black spot, see 114 



