CHEMISTRY. 



93 



woody husk that it ordinarily goes to the bran. 

 Its high percentage of nitrogen corresponds 

 with the extreme tenacity of its sponge and the 

 purity of the bread and crusts baked from it. 

 So far as the analyst can ascertain, the propor- 

 tion of nitrogenous compounds is an unfailing, 

 practical measure of the capacity of flour to 

 make light bread, and to make large and heavy 

 loaves from a given weight. 



A New Metallic Compound. A new metal- 

 lic compound, nam^d Spence's metal, after 

 its discoverer, Mr. J. Berger Spence, has been 

 introduced, which possesses some remarkable 

 and valuable qualities. Its preparation is based 

 on the principle that the sulphides of metals 

 combined with molten sulphur form a liquid 

 which, on cooling, becomes a solid, homogene- 

 ous mass, possessing great tenacity, and having 

 a peculiar dark gray almost black color. 

 Nearly all the metallic sulphides will form, with 

 an excess of sulphur, combinations which have 

 the same properties. A useful form of the 

 metal is made from an ore of iron pyrites con- 

 taining lead and zinc sulphides, and belongs 

 to the class of compounds known as thiates, 

 or sulphur sulphides. The compound has the 

 advantages of a low melting-point, 320 Fahr., 

 of expanding on cooling, of resisting atmos- 

 pheric and climatic influences better than mar- 

 ble or bronze, of superior resistance to acids, 

 alkalies, and water, and of being susceptible of 

 a high polish. A polished surface of the metal 

 has been ex posed for six months in all weathers 

 without showing any change, and an other speci- 

 men suffered but little from a month's soaking 

 in aqua regia. By reason of its low melting- 

 point it is easily prepared for the mold, and in 

 consequence of its power of expanding it gives 

 a nearly perfect cast. In the gelatine mold it 

 yields an impression before the form of the 

 mold is destroyed, and then, if the gelatine be 

 allowed to remain on the metal till it is cooled, 

 it remodels itself so as to be ready for the next 

 casting. It is adaptable to a great variety of 

 uses, for some of which it is superior to lead, 

 and for which its cheapness its cost being es- 

 timated as only about one fourth that of lead 

 gives it great advantages. 



Cold as a Chemical Agent. While heat of 

 temperatures above the freezing-point of water 

 has long been recognized as one of the most 

 powerful agents for producing the chemical 

 operations desired by manufacturers, heat of 

 lower temperatures, or cold, as it is commonly 

 called, has been less generally employed or 

 thought of for such purposes. This agent has 

 been lately made to aid in the manufacture 

 of Glauber's salt, at some French works, with 

 such success as to suggest that its more gen- 

 eral application is possible in other directions. 

 Under a process devised by M. Georges Four- 

 nier, of Paris, the lye from the oxidized pyritic 

 shales of Rheims and Picardy from which alum 

 and copperas were formerly made, containing 

 aluminum sulphate and a portion of iron sul- 

 phate 



is mixed with common salt in such, proportion that 

 there shall be sodium enough to combine with all the 

 sulphuric acid, and chlorine enough to take up all 

 the aluminum and iron. The solution is then exposed 

 to a temperature of from 3 to 5 below the freezing- 

 point, at which the sulphate of soda is almost insolu- 

 ble. That substance is deposited in the ordinary form 

 of Glauber's salt as a fine crystalline sediment, while 

 the aluminum and iron remain in solution as chlorides. 

 The " mother-liquor," or lye, is then run off, and the 

 deposit is washed in brine cooled down to the freezing- 

 point. After it is dried, it is fit for any purpose to 

 which Glauber's salt is applicable. The mother-liquid 

 may be made into a chloride of aluminum, which is 

 valuable for disinfecting purposes. A pure chloride 

 of aluminum, suitable for use in dyeing, and for the 

 destruction of the vegetable matter which is mingled 

 with wool, may be prepared from cake-alum by a sim- 

 ilar cold process. Another French inventor, by ex- 

 posing the lyes of the "sal mixte" of the salt-works 

 of the Mediterranean coast, consisting of common salt 

 and sulphate of magnesia, to a temperature of about 

 11 below the freezing-point, obtains Glauber's salt in 

 deposit with a solution of the chloride of magnesium, 

 a substance largely used for weighting textile fabrics. 



Luminous Paint. The lato Mr. Balmain 

 succeeded in producing from a compound of 

 lime and sulphur a constant and very powerful 

 phosphorescent substance, which he patented 

 and applied as a paint; articles coated with it 

 become luminous after exposure to the light, 

 and retain their glow for a considerable length 

 of time. In a lecture on this substance by Pro- 

 fessor Heaton, its sensitiveness was shown by 

 passing electric sparks in front of a card paint- 

 ed with it which had been previously kept in 

 darkness. Each spark impressed its image on 

 the card, and made it luminous. Even a luci- 

 fer-match struck in front of a dark pane pro- 

 duced a visible effect on the paint. The high- 

 est effect is produced by the violet and ultra- 

 violet rays. The red and yellow rays do not 

 add to the luminosity; in fact, they diminish 

 it when they are allowed to continue to act for 

 a considerable time. A short exposure of the 

 paint to ordinary daylight is sufficient to pro- 

 duce a high degree of illumination, the amount 

 and duration of which will depend considerably 

 on the quantity and quality of the light and on 

 other conditions. When the paint has been 

 exposed to the intense light of the sun or of 

 burning magnesium, a good deal of the brill- 

 iancy disappears quickly, but after that the 

 fading is very slow ; and a more or less useful 

 light will remain through the length of an or- 

 dinary winter's night. The paint appears to 

 be of satisfactory durability as against all weath- 

 ers and the action of sea- water. The useful pur- 

 poses to which it may be applied are almost 

 innumerable. The present cost of the substance 

 is fixed by the manufacturers at twenty-eight 

 shillings, or about seven dollars a pound. One 

 pound will paint about twenty-five square feet 

 of surface. 



Action of Citric Acid on Minerals. Profess- 

 or H. Carrington Bolton, of Trinity College, 

 Hartford, Connecticut, has made investigations 

 of the reactions of two hundred species of min- 

 erals with citric acid, by means of which he 

 has found that that substance has a power of 



