448 PHYSIOLOGICAL CHEMISTRY 



3. Phenylhydrazine Test. Make the test according to directions under Glu- 

 cose, 3, page 22. 



4. Polariscopic Examination. A simple polariscopic examination, when taken 

 in connection with other ordinary tests, will furnish the requisite data regarding 

 the presence of fructose, provided fructose is not accompanied by other levorotatory 

 substances, such as conjugate glycuronates and /3-hydroxybutyric acid. 



ARSENIC 



When any soluble form of arsenic is introduced into the body in 

 any way, it is quickly absorbed and distributed by the blood and 

 lymph. The absorption is influenced by the quantity and quality of 

 the food in the stomach, and the activity of the circulation of the part 

 in contact with the poison. Some of the absorbed arsenic may be 

 returned to the alimentary canal by way of the bile and gastro-intes- 

 tinal mucous membrane. After absorption it may be deposited in the 

 liver, kidneys, brain, bone, muscles, and walls of the stomach and 

 intestines. It is eliminated in all of the excretions, but chiefly by the 

 kidneys and through the feces. It does not appear very promptly in 

 the urine but continues to be excreted in the urine over a long period 

 of time, in some cases for several months. The urine may be examined 

 for arsenic by the following methods. 



i. Marsh and Marsh-Berzelius Method. This method has the advantage of 

 serving as a qualitative and quantitative determination, and is a very delicate test ; 

 it is, however, long and tedious. The various steps in the analysis are: (i) the 

 destruction of the organic matter in the urine; (2) treatment with sulphuric acid to 

 drive off excess nitric acid and break up nitro-compounds; and (3) application of 

 independent test to the resultant solution. Proceed as follows: The urine, to 

 which is added one-third its volume of nitric acid, is placed in a casserole or evapo- 

 rating dish and evaporated at 150 to 160 to a syrupy consistency. The mass is 

 then allowed to cool and 5 c.c. concentrated sulphuric acid added, and gentle heat 

 applied. The heating must be done cautiously, or deflagration takes place and 

 some of the arsenic is sure to be lost. The mass will liquefy and finally darken, 

 indicating organic matter. Cool and add concentrated nitric acid, i c.c., and apply 

 very gentle heat; copious reddish-brown fumes are evolved. Gradually raise the 

 temperature until darkening of the solution occurs, then cool, add i c.c. concentrated 

 nitric acid and again apply gentle heat, and repeat the process until the solution 

 fails to darken. Now raise the temperature until white fumes begin to come off. 

 At this temperature excess nitric acid will have been removed and all nitro-com- 

 pounds broken up. The solution at this point is clear and at most a pale straw color. 

 Cool and add a mixture of 10 c.c. concentrated sulphuric acid and 40 c.c. water, 

 and test for ajsenic using a Marsh apparatus. The apparatus (see Fig. 131, p. 449) 

 consists of a wide-mouth flask 250 c.c. capacity fitted with a two-hole stopper. 

 Through one hole is passed the stem of a separatory funnel of 50 to 60 c.c. capacity. 

 Through the other hole a piece of glass tube bent at right angles, which is fitted to 

 a calcium chloride tube, and this in turn to a narrow quartz tube, the distal end of 



