A microchemical test for choline and its esters in tissue extracts.

ANY simple test, by means of which we can detect small amounts of free choline and distinguish between it and its water-soluble esters in tissue extracts, is of interest. It has been known for a long time that periodide solutions are very delicate precipitants for choline. In 1897 Florence used the periodide reagent in testing for semen. In 1901 Bocarius showed that the test was due to the presence of choline in the semen. Stanek [1905; 1906, 1, 2], using his concentrated potassium tri-iodide reagent and determining the amount of nitrogen in the periodide precipitate, was able to estimate the amount of choline present in plant extracts. Roman [1930] worked with solutions ofpure choline and used a modified Stanek's reagent. He claims to be able to determine accurately amounts of choline ranging from 5y to 5 mg. per 1 ml., by estimating the iodine in the enneaiodide precipitate. Carles and Leuret [1934] have studied the microcrystalline characters of the periodide compounds of choline, betaine and trimethylamine in pure solution. Only scanty data, however, appear in the literature regarding the microscopic characters of choline periodide in tissue extracts. Moreover, there is no account of the microscopic appearances of the periodide compound of any of the choline esters. The present investigation therefore deals with the microcrystalline characters of the periodides of choline and its esters. In all the experiments the solution to be examined was mixed with Florence's reagent on a clean dry microscopic slide in the proportions suggested by Carles and Leuret, i.e. 3 drops of the reagent to 1 drop of the unknown solution. Immediately after covering the preparation, the specimen was examined. The Florence's reagent used had the following composition: potassium iodide 1-65 g.; iodine 2-54 g.; distilled water 30-00 g. All the solutions examined were neutral or acid to litmus.