ELEMENTARY PHYSIOLOGICAL CHEMISTRY 277 



stream of pure hydrogen gas l through the weighing filter, meanwhile 

 warming the tube. When reduction is complete,, the weighing filter is 

 cooled in a desiccator containing hydrogen gas and then weighed. 

 From the amount of copper found the sugar can be read off in specially 

 prepared tables (see Arch. f. d. ges. Physiol. (Pfliiger), Vol. XCVL, 

 p. 105). 



Blood in the Urine Haematuria. If blood be mixed with urine in 

 the kidney it colours the urine brown, since, by being mixed for some 

 time with an acid fluid, the haemoglobin has been changed into 

 methaemoglobin. If the urine be examined by means of the spectro- 

 scope the band in the red, which is almost characteristic of methaemo- 

 globin, will be seen. 



If the haemorrhage be from the bladder or urethra the urine will be 

 coloured red, and will show the spectrum of oxyhaemoglobin. 



The sediment in both these cases will show blood corpuscles under the 

 microscope. Sometimes, however, blood pigment occurs in the urine 

 without corpuscles being present. Such a condition is called 

 Haemoglobinuria, and, since the pigment escapes from the blood in 

 the kidney, it has become changed into methaemoglobin before the 

 urine is voided. Besides the spectroscopic and microscopic tests, there 

 is a very delicate chemical test for blood called the guaiac test. 



EXPERIMENT IX. To about 5 c.c. of urine add two drops of tincture 

 of guaiac. A white precipitate of resin is obtained. Now add about 

 5 c.c. of ozonic ether, and note that a deep blue colour develops at once 

 where the two fluids meet. The reaction is said to be due to oxidation 

 of the guaiac, the haemoglobin carrying the oxygen from the ozonic 

 ether to the guaiac. 



Apply also the appropriate microscopic and spectroscopic tests for 

 blood in urine. 



Bile in the Urine. When the bile duct is blocked by a calculus, or 

 by swelling of its mucous membrane from catarrh, the bile, which 

 accumulates in the bile channels, is reabsorbed into the blood-vessels 

 and carried to the tissues, which become stained with bile pigment. 

 Under these conditions the urine contains bile constituents, the most 

 easily recognised of which are the bile pigments. 



EXPERIMENT X. Apply Gmelin's test (see p. 234) to the urine of a 

 jaundiced patient. Where only a trace of bile is present, the reaction 

 may be made more delicate by first of all filtering the urine through 

 white filter paper, and, when all has filtered through, applying a drop 

 of fuming nitric acid to the stain on the filter paper. The play of 



1 The hydrogen is purified by bubbling it through an acid solution of KMn0 4 , 

 and then passing it through a pumice stone and H 2 S0 4 absorption tube (p. 146). 



