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Water softening by aluminum plates
CURRENT TOPICS.
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charged electroscope, placed above a layer of a salt of one or other of these three metals; when the electroscope was positively charged, it gave an appreciable deflection with potassium or rubidium salts, but no deflection or at best only doubtful, with coesium salts.
Water Softening by Aluminum Plates. T. R. DUGGAN. (Eng. cxi, 3 9 2 . ) - - T h i s method was discovered by Brandes and is known as the " L u m i n a t o r " process. The water is allowed to run down an aluminum plate of special dimensions, with corrugations of a particular size, according to the character of the water under treatment. No chemicals are used; all that is required is to keep the corrugations well brushed and clean from the deposit. When the storage tanks and mains are far from the boiler, they should be coated with a non-conducting composition, and the water shbuld reach the J~iler as soon after treatment as possible. Storage tanks should not be too large, as the water should be used within seven days after treatment to get the maximum effect. When water is passing continuously, day and night, it may be necessary to give the apparatus a rest about one day per week to avoid polarisation of the plates. The passage of the water over the channels at certain speeds induces a current of electricity, the water being negative and the plates positive, and the salts are ionised, and assume the amorphous instead of the crystalline form. At the same time the almninum, through friction and the electrical action, is abraded from the surface as a colloid, which undergoes change in the water. F. G. Donnan found but little almninum hydroxide in the treated water, but the ultra-microscope showed colloidal aluminum mixed with hydroxide. Water thus treated deposits much less scale; old scale is softened and detached from the plates, especially the flues; steam is drier; less coal is needed for steam-raising, and the salts are found as powder in the bottom of the boilei-. It is important that boilers should be regularly blown off, particularly when the apparatus is first installed, as the old scale comes down so rapidly that the plates may become overheated from its accumulation, unless it is quickly removed. After the old scale is removed, this danger ceases, as only mud is found in the boiler, and the water is in contact with the plates and tubes. If the boiler is systematically blown off, little or no mud will be found in it. Priming is much less, or q u i t e eliminated, by the use of this apparatus. B r o n z e and I r o n Articles of the L a T e n e Period.
H. RUPE,
Verh. Natur[. Ges. Basel, xxi, 4 o . ) - - B r o n z e and iron particles from the graves of Tessin were examined. About II per cent. of the bronzes examined contain 9 ° per cent. copper and IO per cent. tin. About 5 per cent. contain only 1. 5 per cent. of tin or less, which indicates they were made from a copper ore containing tin. The anahsis of the iron articles leads to the following deductions
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charged electroscope, placed above a layer of a salt of one or other of these three metals; when the electroscope was positively charged, it gave an appreciable deflection with potassium or rubidium salts, but no deflection or at best only doubtful, with coesium salts.
Water Softening by Aluminum Plates. T. R. DUGGAN. (Eng. cxi, 3 9 2 . ) - - T h i s method was discovered by Brandes and is known as the " L u m i n a t o r " process. The water is allowed to run down an aluminum plate of special dimensions, with corrugations of a particular size, according to the character of the water under treatment. No chemicals are used; all that is required is to keep the corrugations well brushed and clean from the deposit. When the storage tanks and mains are far from the boiler, they should be coated with a non-conducting composition, and the water shbuld reach the J~iler as soon after treatment as possible. Storage tanks should not be too large, as the water should be used within seven days after treatment to get the maximum effect. When water is passing continuously, day and night, it may be necessary to give the apparatus a rest about one day per week to avoid polarisation of the plates. The passage of the water over the channels at certain speeds induces a current of electricity, the water being negative and the plates positive, and the salts are ionised, and assume the amorphous instead of the crystalline form. At the same time the almninum, through friction and the electrical action, is abraded from the surface as a colloid, which undergoes change in the water. F. G. Donnan found but little almninum hydroxide in the treated water, but the ultra-microscope showed colloidal aluminum mixed with hydroxide. Water thus treated deposits much less scale; old scale is softened and detached from the plates, especially the flues; steam is drier; less coal is needed for steam-raising, and the salts are found as powder in the bottom of the boilei-. It is important that boilers should be regularly blown off, particularly when the apparatus is first installed, as the old scale comes down so rapidly that the plates may become overheated from its accumulation, unless it is quickly removed. After the old scale is removed, this danger ceases, as only mud is found in the boiler, and the water is in contact with the plates and tubes. If the boiler is systematically blown off, little or no mud will be found in it. Priming is much less, or q u i t e eliminated, by the use of this apparatus. B r o n z e and I r o n Articles of the L a T e n e Period.
H. RUPE,
Verh. Natur[. Ges. Basel, xxi, 4 o . ) - - B r o n z e and iron particles from the graves of Tessin were examined. About II per cent. of the bronzes examined contain 9 ° per cent. copper and IO per cent. tin. About 5 per cent. contain only 1. 5 per cent. of tin or less, which indicates they were made from a copper ore containing tin. The anahsis of the iron articles leads to the following deductions