186 



REPOKT — 1900. 



methods are adopted, whilst they make colorimetric methods altogether 

 unreliable. 



The electrolytic determination of iron presents the important advan- 

 tage over the above by not being afi'ected by these adverse conditions, 

 and our results justify the conclusion that it is reliable and accurate. 

 The presence of phosphoric acid does not interfere with the determination. 

 Any organic matter present in the solution of the ash can be completely 

 removed by a preliminary electrolysis in presence of sulphuric acid. This 

 was proved in a series of experiments in which the attempt was made to 

 effect the deposition of the metal directly in urine without concentration 

 and ignition of the resulting ash. In order to overcome the frothing due 

 to the decomposition of the urea in the urine, during the electrolysis, the 

 latter was first decomposed with nitrous acid, the details of the method of 

 determination being as follows : 100 c.c. of urine are treated in a flask with 

 12 c.c. of sulphuric acid (1:5) and T) gr. of sodium nitrite, and gently 

 warmed. After the decomposition is complete 5 c.c. of sulphuric acid 

 (cone.) are added, the solution boiled to complete the decomposition of 

 the urea, and electrolysed overnight with a C.D.ioq=1"0 ampere. The 

 urine is completely decolorised by the current, a crystal clear solution 

 resulting, whilst a deposit of carbon quite free from iron takes place on 

 the cathode. The solution is then neutralised with ammonium hydrate, 

 oxalic acid added to acid reaction, then 5 gr. of ammonium oxalate, and 

 boiled. The precipitated calcium oxalate, which does not retain any of 

 the iron, is filtered off, washed, and the filtrate electrolysed either atGO^C. 

 with a CD., no = 1-0 to 1*5 ampere, or, better, overnight, cold, with a 

 CD. 1110 of O'o ampere and 3-0-4-0 volts. It is important not to de- 

 crease the proportion of oxalate, or magnesium carbonate may be 

 formed on the cathode ; it is easily soluble in ammonium oxalate. A 

 platinum spiral of 1 to 5 gr. weight, according to the cjuantity of iron 

 present, is used as the cathode, and a platinum dish of about 200 c.c. 

 capacity as the anode. The deposited metal, which is quite bright and 

 metallic in appearance, after being washed, dried, and weighed, can be 

 dissolved off, and the spiral re-weighed as a check on the determination, 

 whilst confirmatory qualitative tests can, of course, be made with the 

 resulting solution. In the following experiments known weights 

 of iron were added to 100 c.c. of normal mine. (The quantity of metal 

 present in the urine is negligible, less than 0-1 mgr.) A blank experi- 

 ment was first made, with all the reagents employed in the method as de- 

 scribed, to determine the contained iron and to make allowance for the 

 carbon deposited ; the total amounted to 0-2 mgr., which was deducted in 

 all cases. 



The results show that 1 mgr. of iron per 100 c.c. of urine can be very 

 satisfactorily estimated by this method ; but this amount is far in excess 

 of that ever found in normal urine or likely to be present, even under 

 pathogenic conditions. In both cases at least 1,000 to 1,500 c.c. should be 

 used for a determination, and this when concentrated to, say, 200 c.c, is 

 so highly charged with organic matter that even when electrolysed for 



