1 70 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



is converted into creatinine by heating with 1-2 drops of water per gm. of 

 solid in an autoclave at 130-140 for 3 hours. A little boiling water is 

 poured over the residue and alcohol added. Pure creatinine (98-100 per 

 cent.) is obtained. 



S. R. Benedict l finds the following procedure for preparing creatinine 

 from urine more convenient than that described by Folin. At least 10 litres 

 of urine should be used. 



1 8 gm. of picric acid per litre of urine are dissolved in about 50 c.c. of 

 hot alcohol and added with stirring to the urine, which must be fresh. The 

 potassium creatinine picrate which is precipitated is filtered off after about 

 12 hours upon a Buchner funnel and washed once or twice with saturated picric 

 acid solution. The dry, or nearly dry, picrate is decomposed by stirring it in 

 a mortar with concentrated hydrochloric acid (60 c.c. per 100 gm. picrate) for 

 3-5 minutes. The picric acid is filtered off by suction through a hardened 

 filter p?per and washed once or twice with a small quantity of water. The 

 filtrate is transferred to a flask and neutralised with excess of magnesium 

 oxide (commercial, heavy) which is added in small quantities at a time whilst 

 the liquid is kept cold with water. The liquid turns bright yellow when it 

 is neutral and litmus may be used to test the reaction.. The mixture is 

 filtered by suction and the residue is washed once or twice with a little 

 water. The filtrate is acidified with a few c.c. of glacial acetic acid (paying 

 no attention to a precipitate which may form), diluted with 4 volumes of 

 alcohol and filtered after abrut 15 minutes from a small precipitate (chiefly 

 calcium sulphate). The filtrate is treated with a 30 per cent, alcoholic 

 solution of zinc chloride, using 3-4 c.c. per litre of urine employed, stirred well 

 and allowed to stand for 1 2 hours. The precipitate of creatinine zinc chloride 

 is filtered off and washed once, with water, 50 per cent, alcohol and 95 per 

 cent, alcohol. A nearly white product is obtained in a yield of 1-5-1*8 

 gm. per litre of urine. 



Though a 10 per cent, loss is incurred, the creatinine zinc chloride must 

 be recrystallised : 10 gm. of the compound are treated with 100 c.c. of water, 

 about 60 c.c. of N sulphuric acid are added and the mixture is heated till a 

 clear solution is obtained ; 4 gm. of animal charcoal are added and the 

 boiling is continued for i minute. The solution is filtered and the residue 

 is washed with water. The filtrate is transferred to a beaker and treated with 

 3 c.c. of zinc chloride solution and 7 gm. of potassium acetate dissolved in a 

 little water. After 10 minutes the solution is diluted with an equal volume of 

 alcohol and allowed to stand in a cool place. The crystals which separate 

 contain some potassium sulphate ; this is removed by stirring them up twice 

 with their weight of water, washing with water and alcohol. 8*5-9 m - 

 of recrystallised salt are obtained. 



Creatinine is prepared from the recrystallised zinc chloride compound by 

 placing the powdered substance in a dry flask and treating it with seven times 

 its weight of concentrated aqueous ammonia and warming slightly until a clear 

 solution is obtained, avoiding loss of ammonia as far as possible. The flask 

 is stoppered and kept at b. Pure creatinine crystallises out in a yield of 

 60-80 per cent. If it be slightly brown, it may be recrystallised from boiling 

 alcohol, or by dissolving 'it in five times its weight of ammonia as described 

 above. 



1 J. Biol. Chem., 1914, 8, 1813. 



