igii] Carl L. Aisberg 121 



the boiling continued until the precipitate is coarsely crystalline.^ 

 (b) The flask is closed with a rubber stopper and shaken vigor- 

 ously for ten minutes. After this an excess of 3 per cent. am- 

 monium Oxalate is added. 



6. The Solution is cooled to the room temperature and 8 c.c. of 

 20 per cent. sodium acetate added. (In the case of feces-ash, add 

 15 c.c. of acetate Solution.) 



7. The Solution may be either (a) allowed to stand over night, 

 or (b) stoppered and shaken vigorously for ten minutes. 



8. The calcium Oxalate is filtered off on a small ash-free filter 

 and washed free from chloride with 0.5 per cent. ammonium 

 Oxalate Solution. 



9. One of two things may be done here: (a) The precipitate 

 and filter are dried, incinerated in a weighed platinum crucible to 

 CaO, and brought to constant weight before a blast lamp. (b) The 

 excess of ammonium Oxalate from the washing fluid is removed 

 from the calcium Oxalate precipitate by washing four times 

 with cold distilled water, each time Alling the filter about two- 

 thirds füll and allowing the wash water to drain off completely 

 before adding more. A hole is punched in the point of the filter 

 paper with a glass rod and the calcium Oxalate washed down into 

 a flask with a stream of water from a wash bottle. The fluid is 

 brought up to about 50 c.c. in bulk and 10 c.c. of concentrated sul- 

 phuric acid are added. The Oxalate is titrated in the hot Solution 

 (40°-6o° C.) with Standard potassium permanganate Solution. If 

 magnesium is to be determined in the filtrate, the determination 

 may be carried out as described in my earlier paper on the subject. 



Summary of the results of Part II. The results may be sum- 

 marized by describing the details of the method found to be best. 



Solutions needed: 2^/2 per cent. oxalic acid Solution; 20 per cent. 

 sodium acetate Solution. 



1. If the urine is alkaline it is made neutral or slightly acid so 

 that all calcium is in Solution. 



2. The neutral or slightly acid urine is filtered to free it from 

 all detritus and sticky material that may later interfere with filtra- 

 tion of calcium Oxalate. 



' If but little calcium is present it is not necessary to add Oxalate. 



