80 CHEMISTBY. 



well as by other cause?. He compares the action of oil of turpentine in these casca 

 to that ot the blood in respiration. 



Hydrated Silica.^- Liebig has found that the solubility of silica depends essentially 

 upon the circumstance whether or not a sufficient quantity of water for its solution 

 is present at the moment of its separation. If a solution of a soluble silicate, the 

 strength of whiah per cubic centimetre is known, be gradually diluted with measured 

 quantities of water, a point may be arrived at when, on the addition of acid, the 

 fluid remains perfectly clear, and no silica is separated. In this way water can 

 dissolve as much as one five-hundredth of silica. 



Ammonia and its salts materially diminish the solubility of silica. 



Action of Carbonates. — Rose has carefully examined the circumstances under 

 which insoluble or nearly insoluble salts, such as the sulphates of baryta, strontia, 

 a nd lime, &c, are decomposed by alkaline carbonates. When the soluble salt 

 formed is capable of decomposing the insoluble salt produced, the decomposition 

 is hindered, and can only be effected by constant removal of the soluble salt, or 

 employment of an excess of the decomposing salt. 



When no such decomposing action of the resulting soluble salt upon the insoluble 

 one takes place, the decomposition goes on in accordance with the ordinary laws of 

 affinity. An alkalic carbonate decomposes sulphate of baryta, and an alkalic sulphate 

 decomposes carbonate of baryta, hence very imperfect decomposition can be pro- 

 duced from equivalent weights of these salts. An alkalic carbonate can decompose 

 sulphate of strontia, but an alkalic sulphate has no effect upon carbonate of strontia, 

 hence in this case a nearly complete decomposition is effected. The same is the 

 case with the sulphates of lime and lead, and is doubtless connected with the partial 

 solubility of these sulphates, for if the smallest quantity were to be formed and dis- 

 solved in the fluid, it would be immediately decomposed by the action of the 

 alkalic carbonate. 



Cement. — M. Sorel announces the formation of a very hard and durable cement 

 by the action of chloride on oxide of zinc. The analogous chlorides may be substi- 

 tuted for that of zinc. The cement may be poured into moulds like plaster, becomes 

 as hard as marble, is not affected by cold, moisture, or even by boiling water, and 

 is but slowly acted on by strong acids. It has been long used as a cement for 

 stopping teeth. It can also be employed as a very hard and durable paint. 



Strength of Bates. — Rose has found that there is no more certain means of 

 ascertaining the strength or weakness of the basic properties of the different metallic 

 oxides than treating them with solutions of inodorous ammoniacal salts, especially of 

 chloride of ammonium. All metallic bases of the composition 2 R + and R + 

 decompose the ammonia salt, while those of the formula 2 R + 3 0, and others 

 containing still more oxygen are unable to effect the decomposition even after long 

 boiling. The only exception is in the case of glucina, but many chemists have been 

 inclined to rank this among the oxides of the formula R + 0, and very recently 

 Debray has concluded that glucina must be regarded as an earth which has no 

 analogue, standing midway between the bases R + and 2 R + 8 0. 



In a later paper Rose inclines to the formula 2 G+ 3 for glucina. He finds that 

 glucina exposed to the heat of a porcelain furnace forms a dense caked mass, of 

 specific gravity 3 - 02l and exhibiting under the microscope regular prismatic crystals 

 like the native alumina or corundum. Alumina, when heated in the same manner, 

 acquires a density of 399 or 4*0, and if from these numbers the atomic .volumes be 



