128 CHEMICAL PHYSIOLOGY. 



(a.) If blood is suspected, use the spectroscope if the 

 colour appears to indicate the presence of blood. 



(6.) If the colour is such as to suggest the presence of bile, 

 concentrate the fluid on a water-bath, and apply Gmelin's 

 test for the bile-pigments (Lesson IX., 6). If proteids are 

 absent, apply Pettenkofer's test for the bile-acids (Lesson 

 IX., 3). If proteids are present, proceed as in Lesson I., 

 p. 19. 



(c.) In testing for urea, proceed as in Lesson XV., 2, by 

 precipitating with baryta mixture. Filter, evaporate the 

 filtrate to dryness, redissolve the residue with absolute 

 alcohol, and allow some of the alcoholic extract to evaporate 

 on a slide, and use the microscope for the detection of 

 crystals of urea. Apply the other reactions for urea in 

 Lesson XV., 4. 



(d.) For uric acid, or its salts, add hydrochloric acid to 

 precipitate the uric acid in crystals [Lesson XV. 2, (a.)], and 

 to the latter apply the murexide test. 



(e.) If ferments are suspected, their action must be tested 

 on fibrin or starch mucilage, as the case may be, the reaction 

 of the fluid being adapted to the ferment tested for. 



B. If a powder or solid substance be given to you, 



(a.) Examine it with the naked eye and microscopically, 

 whether it be amorphous or crystalline. 



(6.) Burn some in a tube ; smell it to detect any odour. 

 Observe if it leaves an ash. 



(c.) Examine its solubility in water, caustic soda, salt 

 solutions, alcohol, and ether. 



(d.) Apply tests in Lesson I., 1, for proteids. 



(e.) If it contain a proteid, test its solubility in water. 

 Native albumins, peptones, and gelatin are soluble; the 

 others are insoluble. Confirm by other tests in Lesson I. 



(/) If it be not a proteid, or if proteids be present, 

 remove them. Test if it be soluble in cold water, and to the 



