THE ANALYST. 113 TOXICOLOGICAL ANALYSIS. (Oestew. Chem. Zeit., 1902, v., 559.)-The author has reinvestigated the processes described by Rossel (ANALYST, 1902, xxvii., 367) and by Vitali (ibid., p. 329) for the recognition of blood-stains or blood in urine. Vitali's process works perfectly, and the presence of blood on iron, in the presence or absence of rust, or on dried fabrics, can be ascertained with it. As a solvent for the spots, the usual physiological solution of common salt may be employed. It is a matter of complete indifference whether the guaiacum tincture is that of the resin or of the wood; and in contradistinction to the test for heated milk fresh tinctures Detection of Blood. Utz.114 THE ANALYST. work as well as old ones; very old specimens, however, were not investigated.Nevertheless, Utz considers it advisable to carry out a confirmative test, either on 8, sample known to contain blood or by means of Rossel’s reaction. I n the Rossel test, after the ether has been shaken with the reagent and the liquid has settled, the aqueous layer is at first orange, but gradually changes to red. Utz has never found a cherry red to appear in ten minutes ; it requires much longer to develop-sometimes an hour if the proportion of blood present is small. It may, however, be hastened by allowing the mixture to rest quietly for fifteen or twenty minutes and then shaking it briskly. Generally the aqueous layer then appears pale carmine red, the ether having a faint wine-yellow colour. Vitali’s test is the more delicate, rapid, and distinct of the two; but Rossel’s reaction is specially suitable for corroborative evidence, particularly when there is not sufficient of the sample to examine in the spectroscope, when the formation of Teichmann’s haemin crystals is impossible, or when there is no serum to investigate.F. H. L. Notes on the Reactions of Blood with Guaiacum and Aloin. E. Schaer. (Zezt. a n d Chem., 1903, xlii., ‘i-lO.)-The blue coloration produced by the action of hydrogen peroxide or ozonized ” turpentine oil upon guaiaconic acid in the presence of an oxygen-carrying substance in the colouring matter of the blood has frequently been condemned as a test for blood-stains, on the ground that many other substances, e.g., enzymes and oxidizing metallic salts, produce the same results. In the author’s opinion, however, it is reliable if proper precautions be taken. Under analogous conditions aloin (barbaloin and natalaloin) forms a red com- pound, aloin red, which will afford confirmatory evidence, though control experiments must also be made in this case. The test is applied by extracting the blood-stains (even when very old) with a concentrated (70 to 75 per cent.) solution of chloral hydrate, mixing the extract with a weak solution of aloin and chloral hydrate, and pouring on to the surface of the liquid either <‘ ozonixed ” turpentine oil, or, for a more rapid reaction, hydrogen peroxide solution. In a short time a violet-red zone is formed, which gradually changes into a red coloration of the aloin solution. (Cf. ANALYST, xxiv., 266.) C. A. M.