1871.] Chemical Science. 401 



show that they might have been predicted. Sodium appears white to the eye, 

 but with the white light reflected from its surface to the eye there are always 

 mingled red rays. If most of the incident white light were normally decom- 

 posed, sodium would appear as a brilliant red metal. Ammonia favours 

 such a decomposition probably by reducing the density and opacity of the 

 surface, and thus the concentrated solution of sodium is lustrous copper-red 

 by reflected light. What should be the colour by transmitted light ? Not red, 

 for the red rays do not penetrate the substance ; the colour must be looked for 

 in that which is complementary to red ; it must be blue or yellow, or combina- 

 tions of these. A continuance of the argument will bring the conclusion that 

 the colour by transmitted light will be blue. Intense blue tinctorial substances, 

 like aniline blue, indigo, and Prussian blue, all illustrate the phenomena of 

 colour of the sodium solution ; they are metallic red when concentrated, and if 

 the solvent be applied in vapour as in the sodium-dissolving experiment, there 

 will be the same modification of colour exhibited. Sodium has a remarkable 

 tinctorial power, which seems not to be surpassed by that of any of the aniline 

 colours. 



Referring to what was said in our January number, p. 127, about the earth- 

 eating of the Javanese and the miners about Wurtemburg, a correspondent 

 gives us the following interesting particulars : — He writes that an old gentle- 

 man, a friend of his, who was born and bred at Dunsire, near Dolphinton, in 

 Lanarkshire, said that when a boy at school there, he and his schoolfellows 

 used to eat a sort of clay which they found somewhere near the banks of the 

 little river Medwin. He described it as of a light brown colour ; it broke into 

 thin plates about like thin oat-cake, was of a sweetish taste, and melted in 

 the mouth. Perhaps it is yet to be found in that neighbourhood ; and, if so, 

 we should be very glad to have a sample for examination. 



Gunning has discovered, in acetate of zinc, a reagent that precipitates the 

 slightest traces of the colouring matter of blood from solutions, even where 

 the liquids are so dilute as to be colourless. Blood, washed from the hands in 

 a pail of water can readily be detected in this way. The flocculent precipitate, 

 thrown down by acetate of zinc, must be washed by decantation, and finally 

 collected on a watch-glass, and allowed to dry, when the microscope will 

 readily reveal haemin crystals if any blood be present. 



The artificial preparation of coniine, an oily liquid, highly poisonous, and 

 closely resembling the nicotine obtained from tobacco, has more than ordinary 

 interest, as it suggests the possibility of our being able to make other alkaloids, 

 such as quinine, morphine, and the like ; and if we can succeed in this, why not 

 prepare the less complex compounds, sugar, starch, &c. ? Coniine has been 

 artificially prepared by Hugo Schiff, by heating alcohol and ammonia at 210 , 

 together with butyraldehyd, precipitating with a platinum salt, and distilling 

 the product. The artificial alkaloid exhibits the same properties as the native, 

 and is a violent poison. As the first step in the synthesis of vegetable 

 alkaloids, the discovery of Professor Schiff is one of the most important in 

 modern chemistry. 



Recent occurrences have rendered anything connected with the consumption 

 and production of food a matter of great interest. In a public lecture 

 delivered at the Medical School at Paris, for the purpose of imparting some 

 sound knowledge on the quantity of food required to keep man in a vigorous 

 and healthy state, Dr. See said that the daily ration for an adult might be enu- 

 merated as follows : — 100 grms. of meat, 20 grms. of salt fish, 750 grms. 

 of bread, 50 grms. of lard, and 50 grms. of dried and compressed vegetables — 

 a total of 970 grms. of solid food, containing 88 grms. of albuminous matter. 

 Incidentally, the author observed that crust of bread contains just twice more 

 nutrimental value than crumb, which contains 44 per cent of water. The 

 highly nutritive value of wine was specially alluded to, and illustrated by the 

 fact that, in some districts of France and Spain, men live on bread and wine 

 only for many weeks together in a healthy and vigorous state. 



Some experiments have been made with dogs on the influence which coffee 

 and cacao exert as food, in which Dr. Rabuteau gave diets in one case 



VOL. VIII. (O.S.) — VOL. I. (N.S.) 3 F 



