THE ANALYST. 159 ORGANIC ANALYSIS. Estimation of Potato Starch (Granulose). A. Kaiser. (Chem. Zed., 1902, xxvi., 180.)-The sample is gelatinized in water in the usual way, so as to form a solution of about 1 per cent. strength, and this must be newly made. Fifty C.C. of the liquid are mixed with 10 grammes of sodium acetate, warmed to 50" C., and then precipitated with 25 C.C. of a solution containing 5 grammes of iodine and 10 grammes of potassium iodide per litre, taking care that a small excess of iodine is present. When the precipitate has settled it is collected on a tared paper and washed with a solution of 3 grammes of sodium acetate in 100 C.C. of water. It is next rinsed by means of alcohol into a porcelain basin, and gently warmed with about 5 C.C. of 5 per cent. alcoholic potash until the change of colour shows that the iodide of starch has decomposed.Sufficient excess of alco- holic acetic acid is then added, and after standing some time (the starch retains alkali with much persistence) it is brought on to the same paper as before, washed with hot spirit, absolute alcohol, and ether, and finally dried for four hours at 120' C. The starch so obtained should be weighed between watch-glasses because of its hygroscopicity; and its purity should be tested by its complete solubility in water, any insoluble cellulose, etc., being dried, weighed, and deducted. F. H. L. A Method of Determining the Solubility of Alkaloids. R. A. Hatcher. (Amer. Journ. Pharm., 1902, lxxiv., 134-137.)-This method is intended for deter- mining the solubility of alkaloids which do not readily dissolve in water : 0.1 gramme of the alkaloid is rubbed with water so as to form a smooth paste, and then with more water until a smooth mixture of about 9 C.C.is obtained. To this is added from a burette sufficient normal sulphuric acid to just convert the alkaloid into sulphate, and then sufficient water to make 10 C.C. in all. Portions of 1 C.C. each of this solution are diluted with different proportions of water, and a slight excesB of normal sodium hydroxide solution added to each, the solubility being estimated from the relative amounts of precipitate. Two fresh portions of 1 C.C. are then diluted approximately to the neutralization point, one being taken slightly above and the other slightly below that found in the first determination, and the sodium hydroxide added as before.Finally, a third determination based on the second results will give the solubility by taking the mean between the highest result giving al precipitate and the lowest showing none. Thus, in the case of cinchonine, a slight precipitate was observed on adding a slight excess of sodium hydroxide to a solution of the sulphate containing 1 part in 22,000, but none in that containing 1 in 24,000, and the solubility was therefore taken as 1 in 23,000. Applying the test to morphine, the solubility of which is known to be 1 in 4,350,160 THE ANALYST. the author found that on diluting the portions of 1 c.c., and then adding a very slight excess of alkali, a slight turbidity was given with the liquid diluted to 43 c.c., but none with that diluted to 44 C.C.The solubility was therefore taken as the mean of these results, or 1 part in 4,350. C. A. M. Detection and Estimation of Lactic Acid in the Gastric Juice. A. C. Vournasos. (Zeits. f. angew. Chem., xv., 172.)-For the detection of lactic acid the author makes use of a reagent containing iodine and methylamine. Ealf a gramme of potassium iodide is dissolved in 50 C.C. of water, 1 gramme of iodine is added, the mixture is well shaken, then filtered, and 5 grammes of methylamine are added. Of the gastric fluid under examination, 5 C.C. are filtered and, if viscous, diluted. It is made strongly alkaline by the addition of a little 10 per cent. potash solution, then 1 C.C. of the above reagent is added. The lactic acid is converted into iodoform, which, with the methylamine, gives isocyanide : 2C3Hs03 + 5K20 + 121 = 4HC02K + 6KI + 2CH1, + 3H20 CHI, + 3KH0 + CH3NH2= 3KI + CHSNC + 3H2O.The penetrating smell of the isocyanide enables one to detect 0.005 per cent. of lactic acid. If less than that quantity be present, a larger amount of the sample should be taken and extracted with ether, the ether extract evaporated, and the residue tested as above. If volatile fatty acids are present, the gastric juice should be evaporated at 100" C. to a third of its volume. For the gravimetric estimation of the lactic acid take 30 C.C. of the sample, and evaporate it to one-third. Then mix in a retort with 15 C.C. of aqueous caustic potash and 0.5 gramme of sublimed iodine. The mixture is distilled cautiously into a cooled receiver until & have passed over.The distillate contains the whole of the iodoforrn from the lactic acid present. The iodoform may be collected on a tared filter, washed with water, and dried at 60" C. to constant weight. To the distillate obtained as above are added 50 C.C. of water and the same quantity of 10 per cent. alcoholic potash solution. The mixture is stirred till clear, then titrated with decinormal silver nitrate solution by an application of the precipitation method for iodides. The determination may also be made volumetrically. A. M. ___ . - _ _ - . - __ The Detection of Indican i n Urine. (Joum. Pharm. Chim., 1902, xv., 277-279.)-1n testing urine for indican the blue coloration is sometimes masked by a violet colour, due to the presence of iodine. In such cases the following modification is recommended : The urine is mixed with an equal volume of hydrochloric acid and shaken with a few C.C. of chloroform and a few drops of a dilute solution of sodium hypochlorite. The acid layer is removed by means of a pipette, and the chloroform washed with water and then rendered just alkaline by the addition of a few drops of potassium hydroxide solution. The violet colour due to the iodine disappears, and Bertault.THE ANALYST. 161 the chloroform remains blue in the presence of indican, or becomes colourless in its absence. Care must be taken not to add too large an excess of hypochlorite. C. A. M.