On the Preparation of Creatine, Creatinine and Standard Creatinine Solutions

In order to enlarge the scope of the calorimetric method for the determination of creatinine and creatine it is, I think, necessary to replace the bichromate standard with standard creatinine solutions, and in the next two papers will be described various adaptations of the method based on this principle. In connection with this work I have again gone over the subject of the preparation of creatine and creatinine from urine in order to render more easy their preparation on a large scale as well as to facilitate the preparation of standard creatinine solutions. The precipitation of creatinine from urine. The precipitate obtained on adding picric acid to urine consists to a very large extent of the double picrate of creatinine and potassium (C4H7N30. C$HZ(NO&OH. CBH2(NO&OH) containing 18.55 per cent creatinine. This compound is extraordinarily insoluble so that practically all the creatinine of the urine is thrown out of solution by the picric acid even if no large excess of picric acid is added. If a large excess of picric acid is added the above compound is obtained in less pure condition because potassium and sodium are also precipitated and the total amount of creatinine precipitated cannot be materially increased by this means because it is practically quantitative without it. For the precipitation of creatinine from human urine the following process is satisfactory. To 8 liters of urine in a large precipitating jar add with stirring 60-80 grams of picric acid (8-10 grams per liter) dissolved in 400 cc. of hot alcohol and let the mixture stand over night. Remove the supernatent liquid with a siphon and wash the precipitat,e on a Buchner funnel with cold water.