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Silicon castings
• 57 o,
CURRENT TOPICS.
[J. F. I.
• :,Error s in the Interpretation of T e s t s for Electrolysis in Iron Pipes. C. HERINC. (Elect. Rly. Journ., xlii, II35.)--It is shown in this article" that the interpretation of results obtained by the usual ~tests for electrolysis on underground metal pipes requires great caution, tn-a number of cases it is quite easy to draw misleading conclusions unless the conditions are examined with great care. A considerable difference of voltage between adjoining pipes may mean that there is no actual danger, as everything depends on the nature and resistance of the surrounding soil. The so-called " indirect " method, using voltmeter and ammeter, and determining the voltage across t h e iron pipe both with the ammeter connected and disconnected, is also fallacious; the voltage producing the current may originate at some distant point, and in that case it is easily seen that the resistance of the ammeter itself may seriously affect the figures. Other instances are given where it is shown that the readings, taken by an unskilled observer, are very liable to misinterpretation; and even if this should not be so, there is still to be said that such readings often have no true bearing on the point under examination. T h e T e s t i n g of Materials. ANON. (Bur. of Standards, Circ. 45.)--This circular gives information on the general aspects of • the subject valuable to the user or buyer of materials. A brief outlineis given with regard to each class of material of the tests usually made, the conditions under which such work is undertaken, and some of the limitations. The classes of materials include metals, cements and concrete, ceramic materials, inks, paper, textiles, rubber, leather, lubricating oils and greases, chemicals and miscellaneous technical materials.
Tobacco Growing in Great Britain. ANON. (Times, Aug. 6, I912.)--The Government has accepted an amendment which exempts from payment of excise duty all tobacco grown in this country by responsible persons under licenses from the Treasury, for the extraction therefrom of nicotine to be used in the preparation of insecticides or otherwise for purely agricultural or horticultural purposes. Silicon Castings. T. B, ALLEN. (U. S. Pat. I,O73,56o.)--Allen purifies the silicon which, made in electric furnaces, contains oxide, oxygen and nitrogen and yields porous castings full of blow-holes, by means of metals which deoxidize and remove nitrogen, such as Ca, Mg, V. The silicon is tapped from an electric furnace into a graphite crucible placed in an oil or coke furnace, in which the silicon is kept fluid for a few hours. From 0. 5 to 3 per cent. of Mg is added to the Si in the crucible, until no further reaction is observed. The mould is made of sand and coated with talc. The castings resist acids and are suitable for chemical ware.
CURRENT TOPICS.
[J. F. I.
• :,Error s in the Interpretation of T e s t s for Electrolysis in Iron Pipes. C. HERINC. (Elect. Rly. Journ., xlii, II35.)--It is shown in this article" that the interpretation of results obtained by the usual ~tests for electrolysis on underground metal pipes requires great caution, tn-a number of cases it is quite easy to draw misleading conclusions unless the conditions are examined with great care. A considerable difference of voltage between adjoining pipes may mean that there is no actual danger, as everything depends on the nature and resistance of the surrounding soil. The so-called " indirect " method, using voltmeter and ammeter, and determining the voltage across t h e iron pipe both with the ammeter connected and disconnected, is also fallacious; the voltage producing the current may originate at some distant point, and in that case it is easily seen that the resistance of the ammeter itself may seriously affect the figures. Other instances are given where it is shown that the readings, taken by an unskilled observer, are very liable to misinterpretation; and even if this should not be so, there is still to be said that such readings often have no true bearing on the point under examination. T h e T e s t i n g of Materials. ANON. (Bur. of Standards, Circ. 45.)--This circular gives information on the general aspects of • the subject valuable to the user or buyer of materials. A brief outlineis given with regard to each class of material of the tests usually made, the conditions under which such work is undertaken, and some of the limitations. The classes of materials include metals, cements and concrete, ceramic materials, inks, paper, textiles, rubber, leather, lubricating oils and greases, chemicals and miscellaneous technical materials.
Tobacco Growing in Great Britain. ANON. (Times, Aug. 6, I912.)--The Government has accepted an amendment which exempts from payment of excise duty all tobacco grown in this country by responsible persons under licenses from the Treasury, for the extraction therefrom of nicotine to be used in the preparation of insecticides or otherwise for purely agricultural or horticultural purposes. Silicon Castings. T. B, ALLEN. (U. S. Pat. I,O73,56o.)--Allen purifies the silicon which, made in electric furnaces, contains oxide, oxygen and nitrogen and yields porous castings full of blow-holes, by means of metals which deoxidize and remove nitrogen, such as Ca, Mg, V. The silicon is tapped from an electric furnace into a graphite crucible placed in an oil or coke furnace, in which the silicon is kept fluid for a few hours. From 0. 5 to 3 per cent. of Mg is added to the Si in the crucible, until no further reaction is observed. The mould is made of sand and coated with talc. The castings resist acids and are suitable for chemical ware.