300 URINE. [CH. XII. 



Allow to stand over-night and syphon off the supernatant fluid. Drain the 

 residue on a Buchner funnel and wash with cold saturated picric acid and 

 then drain dry. 



(ii.) Decomposition of the pier ate. 



Treat the dry creatinine pi crate with concentrated hydrochloric acid in a 

 mortar, using Go cc. of acid for every 100 grams, of the picrate. Stir thoroughly 

 with the pestle for 5 minutes. Filter by suction, using a hardened filter paper. 

 Wash residue twice with enough water to cover it, sucking dry each time. 

 Transfer the filtrate at once to a large flask and neutralise with solid heavy 

 magnesium oxide. Add it in small amounts at a time, cooling under the tap 

 after each addition. The solution turns light yellow when all the acid has been 

 neutralised. Filter with suction and wash the residue twice with water. At 

 once add a few cc. of glacial acetic acid to the nitrate and pour it into 4 volumes 

 of 95 per cent, alcohol. Allow to stand at least 15 minutes and filter under 

 suction. 



(iii.) Preparation of creatinine zinc chloride (C t H^N s O) 2 .ZnCl 2 . 



Treat filtrate with a 30 per cent, solution of zinc chloride, using 3-5 cc. 

 for each litre of urine taken. Allow to stand over night in a cool place. Pour 

 off the supernatant fluid and then collect the creatinine zinc chloride in a 

 Buchner. Wash once with water, then thoroughly with 50 per cent, alcohol, 

 then 95 per cent, alcohol and dry. The product should be a nearly white, light 

 crystalline powder. 



Yield: 1-2 to 1-5 grams, per litre of urine. 



(iv.) Recrystattisation of creatinine zinc chloride. 



10 grams, are treated with 100 cc. of distilled water and then with 60 cc. of 

 N. sulphuric acid. The solution is heated to boiling till a clear solution is 

 obtained. About 4 grams, of pure decolourising charcoal are added and the 

 boiling continued for about i minute. The solution is filtered off through a 

 small Buchner, the filtrate being refiltered through the same funnel two or 

 three times till it is quite clear. The residue is washed with a little hot water 

 and the total filtrate transferred to a beaker. It is then treated hot with 3 cc. 

 of a strong solution of zinc chloride and about 7 grams, of potassium acetate dis- 

 solved in a little hot water. After 10 minutes the solution is treated with an 

 equal volume of strong alcohol and allowed to stand for some hours in a cool 

 place. The crystals are filtered off and stirred up with about twice their 

 weight of cold water, filtered, washed with a little water, and then with 

 alcohol. 



Yield : 85 to 90 per cent, of the crude material. 



(v.) Conversion of the zinc chloride compound to creatinine. 



The powdered, recrystallised compound is placed in a dry flask and 

 treated with 7 cc. of concentrated aqueous ammonia for every gram, taken. 

 It is slightly warmed and gently agitated until a clear solution is obtained, 

 care being taken to drive off as little ammonia as possible. The flask is 

 then stoppered and placed in an ice box for an hour or two. Pure creatinine 

 crystallises out. 



Yield : 60 to 80 per cent, of the theoretical. 



362. Jaffe's test for creatinine. To 5 cc. of urine add a few 

 drops of a saturated aqueous solution of picric acid and of a 10 per 

 cent, solution of sodium hydroxide. A red colouration is produced 

 owing to the formation of picramic acid. 



