8 THE ELIMINATION OF CAFFEIN. 



entire period, examined by an improved and more accurate method of 

 analysis, contained 6.6 per cent of caffein, thus indicating that the 

 dog may eliminate an appreciable quantity of caffein unchanged. 



Albanese (1) examined the urine collected in thirty days from one 

 dog which had received 42.5 grams of caffein. The alcoholic extract 

 of the urine after evaporation was suitably treated and precipitated 

 with phosphomolybdic acid in the presence of sulphuric acid. The 

 precipitate was extracted with chloroform several times and crystal- 

 lized. The product thus obtained, which weighed 0.5 gram, did not 

 respond to the caffein tests. Another experiment was tried in which 

 a dog received 3 grams of caffein in five days. Symptoms of poisoning 

 appeared in this case. The urine was examined for caffein by 

 Draggendorff's method, which was somewhat modified. Only traces 

 of caffein were found in this case. Similar experiments carried out 

 on one rabbit and on man also showed the presence in the urine of 

 traces of a substance which was identified as caffein by mere color 

 reactions. 



According to this review of the literature, part of the caffein is 

 eliminated unchanged in animals and in man. As the analytical 

 methods employed, however, are far from satisfactory, the results 

 obtained by most of the writers on this subject are not convincing. 

 It will be noticed, for example, that no proof was brought forward 

 of the presence of caffein other than the identification of its crystals. 

 The melting point was not determined in any of the analyses. 



The necessity of reinvestigation of the subject with special ref- 

 erence to the method of analysis (as well as a study of the channels 

 of elimination of caffein) was therefore obvious. The other ques- 

 tions pertinent to the subject which also suggest themselves will be 

 stated in the following chapter. 



METHODS OF ANALYSIS AND PLAN OF WORK. 



The method employed for the isolation of the caffein in the present 

 research was a modification of the Draggendorff scheme, in which 

 after clarification with lead subacetate solution the caffein was 

 extracted with chloroform and purified by the formation of the 

 periodid. This was decomposed with sulphurous acid and the 

 caffein again extracted with chloroform. In this way the caffein 

 was obtained in a state of high purity, it being possible to recover 

 as little as 0.5 mg quantities from the fluids and tissues of the body 

 by giving careful attention to the purity of the solvent, the proper 

 conditions for the quantitative precipitation of the periodid, etc. 

 The caffein thus obtained by control tests corresponded closely in 

 melting point with pure caffein. As a further test of purity sub- 

 limation was resorted to, the beaker in which it was contained was 

 weighed and remained clean with its original tare, so that for this 



