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Hydraulic cements
.Hydraulic Cements.
40T
scarcely sensible. Thus an electro-magnet, hav~ng an iron core 4~centimetres long and 7 millimetres in diameter, carrying a single row of spires of fine wire 0"277 ram. diameter, in all 103 spires, supported under the influence of two small Bunsen couples, 3'9 kil., while the same core wrapped with a covered wire, supported only 2"4 kil. It is true that but 77 turns of the covered line could be put upon the core. The effects at a distance was still more favorable to the uncovered wire. It is to be observed that if more than one thickness of wire coil is pat over the core, the different thicknesses must be carefully insulated from each other by paper. The wire, too, must be insulated from the core by paper, silk, or wood. After a very careful study of the phenomena, showing that in order to produce these effects, the uncovered wire must be acted on by a battery arranged collaterally, or for quantity, and that with a battery arranged consecutively, (or for intensity,) the covered wire resumes its superiority, M. Du Monecl suggests that the phenomena depend upon a great number of minute currents, which are drawn from the main current at the points of contact of the turns of the wire, the main current following the wire, however, because in that direction the resistance is much the least. For this same reason these minute currents move around the wire instead of across it, and thus add considerably to the influence on the core, while they entirely prevent the induction effect by which is produced the annoying spark and countercurrent at making and breaking connexion. He finishes his essay as follows : " I t results from all these experiments that quantity currents are particularly suited to electro-magnets with uncovered wire, and that their best effects are shown when the insulation of the bobbins is not too great and when the surface of tim battery is in proportion to the number of turns of the wire.
Hydraulic Gements. It has been for along time a matter of reproach to practical science, that notwithstanding the great importance of the subject of cements, and the number of theoretical and experimental researches upon the subject by eminent engineers, we were still left to the most vague hypotheses upon the subject, and no competent c h ~ i s t appears to have interested himself in the matter. M. Fremy has done away with this reproach, as far as he is concerned, in a memoir presented to the French Academy of Sciences~ a digest of which is published in their proceedings of the 15th of May. ¥icat assumed the formation of a double silicate of alumina and lime, which, by absorbing water~ x~as the cause of the setting of the hydraulic cements~ and this view seemed to be confirmed by finding in the calcined cements a silicate which formed a gelatinous precipitate with an acid, which silicate did not pre-exist in the stone before calcination.
408
,Mechanics, Physics, and Chemistry.
MM. Rivet and Chatonav in an important investigation of cements~ to which M. Fremy gives the highest praise, suggested that the calcination of the argillaceous limestone gave rise to an aluminate of lime having the formula Al~0s3Ca0, and to a silicate of lime represented by Si0a3Ca0 , which salts brought into contact with water form hydrates each with six equivalents of water, and thus cause the settling. The result of the experiments of M. Fremy is that the settling of cements is due to two different chemical actions : First, to the hydration of the aluminates of lime ; and, secondly, to a puzzuolanic action, in which the hydrates of lime combine with the silicates of lime and alumina. In the course of his experiments, M. Fremy found that alumina is even a better flux for lime than silica, and he suggests that the very basic compounds of these two substances, those, for instance, containing from 80 to 90 per cent of lime may be useful in the iron furnace, owing to their disposition to absorb sulphur and phosphorus, and thus free the metal from these noxious impurities. He also finds that no substance is capable of acting as a puzzuolana except the simple or double silicates of lime containing only from 30 to 40 per cent. of silica, and sufficiently basic to form a gelatinous precipitate with acid.
TILe t'unctlons of .Leaves of _Plants. The Proceedings of the French Academy of Sciences contain a communication from M. Boussingault on the subject of the functions of the leaves of plants, which will be of much interest to physiologists. The following is the summary of the results of his experiments: 1. Leaves exposed to the sun-light do not decompose pure carbonic acid, or, if they do, do it with extreme slowness. 2. Under the same circumstances in a mixture of carbonic acid and atmospheric air, they decompose the acid rapidly. The atmospheric air appears to have no active part in this phenomenon. 3. Leaves exposed to the sun rapidly decompose carbonic acid when mixed either with nitrogen or with hydrogen. Although the decomposition of the acid is a phenomenon of dissociation, M. Boussingault traces a pretty close analogy between it and the slow combustion of phosphorus.
~ew _Electric Battery. M. Du Chemin, who, in a preceding communication to the Academy of Sciences of Paris, had announced that he had. succeeded in replacing :Nitric acid in the Bunsen battery by Perchlorlde of Iron~ and the Sulphuric acid by Chloride of Sodium, writes to announce that by substituting for the latter salt the impure Chloride of Potassium of commerce, he has succeeded in increasing the motive and electric force~ and that in this way the electric light may easily be obtained.
40T
scarcely sensible. Thus an electro-magnet, hav~ng an iron core 4~centimetres long and 7 millimetres in diameter, carrying a single row of spires of fine wire 0"277 ram. diameter, in all 103 spires, supported under the influence of two small Bunsen couples, 3'9 kil., while the same core wrapped with a covered wire, supported only 2"4 kil. It is true that but 77 turns of the covered line could be put upon the core. The effects at a distance was still more favorable to the uncovered wire. It is to be observed that if more than one thickness of wire coil is pat over the core, the different thicknesses must be carefully insulated from each other by paper. The wire, too, must be insulated from the core by paper, silk, or wood. After a very careful study of the phenomena, showing that in order to produce these effects, the uncovered wire must be acted on by a battery arranged collaterally, or for quantity, and that with a battery arranged consecutively, (or for intensity,) the covered wire resumes its superiority, M. Du Monecl suggests that the phenomena depend upon a great number of minute currents, which are drawn from the main current at the points of contact of the turns of the wire, the main current following the wire, however, because in that direction the resistance is much the least. For this same reason these minute currents move around the wire instead of across it, and thus add considerably to the influence on the core, while they entirely prevent the induction effect by which is produced the annoying spark and countercurrent at making and breaking connexion. He finishes his essay as follows : " I t results from all these experiments that quantity currents are particularly suited to electro-magnets with uncovered wire, and that their best effects are shown when the insulation of the bobbins is not too great and when the surface of tim battery is in proportion to the number of turns of the wire.
Hydraulic Gements. It has been for along time a matter of reproach to practical science, that notwithstanding the great importance of the subject of cements, and the number of theoretical and experimental researches upon the subject by eminent engineers, we were still left to the most vague hypotheses upon the subject, and no competent c h ~ i s t appears to have interested himself in the matter. M. Fremy has done away with this reproach, as far as he is concerned, in a memoir presented to the French Academy of Sciences~ a digest of which is published in their proceedings of the 15th of May. ¥icat assumed the formation of a double silicate of alumina and lime, which, by absorbing water~ x~as the cause of the setting of the hydraulic cements~ and this view seemed to be confirmed by finding in the calcined cements a silicate which formed a gelatinous precipitate with an acid, which silicate did not pre-exist in the stone before calcination.
408
,Mechanics, Physics, and Chemistry.
MM. Rivet and Chatonav in an important investigation of cements~ to which M. Fremy gives the highest praise, suggested that the calcination of the argillaceous limestone gave rise to an aluminate of lime having the formula Al~0s3Ca0, and to a silicate of lime represented by Si0a3Ca0 , which salts brought into contact with water form hydrates each with six equivalents of water, and thus cause the settling. The result of the experiments of M. Fremy is that the settling of cements is due to two different chemical actions : First, to the hydration of the aluminates of lime ; and, secondly, to a puzzuolanic action, in which the hydrates of lime combine with the silicates of lime and alumina. In the course of his experiments, M. Fremy found that alumina is even a better flux for lime than silica, and he suggests that the very basic compounds of these two substances, those, for instance, containing from 80 to 90 per cent of lime may be useful in the iron furnace, owing to their disposition to absorb sulphur and phosphorus, and thus free the metal from these noxious impurities. He also finds that no substance is capable of acting as a puzzuolana except the simple or double silicates of lime containing only from 30 to 40 per cent. of silica, and sufficiently basic to form a gelatinous precipitate with acid.
TILe t'unctlons of .Leaves of _Plants. The Proceedings of the French Academy of Sciences contain a communication from M. Boussingault on the subject of the functions of the leaves of plants, which will be of much interest to physiologists. The following is the summary of the results of his experiments: 1. Leaves exposed to the sun-light do not decompose pure carbonic acid, or, if they do, do it with extreme slowness. 2. Under the same circumstances in a mixture of carbonic acid and atmospheric air, they decompose the acid rapidly. The atmospheric air appears to have no active part in this phenomenon. 3. Leaves exposed to the sun rapidly decompose carbonic acid when mixed either with nitrogen or with hydrogen. Although the decomposition of the acid is a phenomenon of dissociation, M. Boussingault traces a pretty close analogy between it and the slow combustion of phosphorus.
~ew _Electric Battery. M. Du Chemin, who, in a preceding communication to the Academy of Sciences of Paris, had announced that he had. succeeded in replacing :Nitric acid in the Bunsen battery by Perchlorlde of Iron~ and the Sulphuric acid by Chloride of Sodium, writes to announce that by substituting for the latter salt the impure Chloride of Potassium of commerce, he has succeeded in increasing the motive and electric force~ and that in this way the electric light may easily be obtained.