Preparation and Test In G Of Silver-Protein Compounds

Abstract

Silver derivatives of the protargol type were made from 13 different commercial peptones. The peptone samples were purified by precipitating with an ethanol concentration of 75%, reprecipitating once, and discarding any water-insoluble material. A 20–22% solution of the purified material in water, allcalinized with 2 ml. of strong ammonia per 100 ml., was precipitated by adding an equal volume of 25% aqueous AgNO3, and stood in a refrigerator overnight. Thorough washing of the precipitate with distilled water, draining, and then dissolving it in a purified peptone solution (30–35% aqueous), whose volume was 0.6 that of the solution used for silver precipitation, gave the soluble silver derivative. Ammonia was added to facilitate solution and the final pH adjusted to 8.0–8.4. The concentrated solution was dehydrated either with acetone or in a dessicator under reduced pressure and ground to a powder. Staining tests on neurological tissue showed that the Pharmaceutical peptone (Cudahy Packing Co., Omaha, Nebr.) and the Bacteriologic peptone (Wilson Laboratories, Chicago, 111.) gave the best preparations for staining nerve fibers, and that these were essentially equal to the formerly available German made Protargol.