T H E f O U R N A f , OR I N D U S T R I A L A N D ENGIi'1'EERISG C H E M I S T R Y .
542
x G x=-139.86 L =
--
0.60 x N L
y =
--S
5.090 x G 0.0213 x N
=-
The manufacturers of both sheets and wire publish small handbooks which may be had for the asking, giving the gauge, relation of weight to area and length and other data for further calculations. The following results obtained b y this method on three samples of No. 9 gauge wire are fairly representative of the accuracy attainable: LENGTHO F TEST SPECIMENS, THREE INCHES Sample Loss of No. 1. weight. Analysis 1 . . . . 0.1030 Analysis 2. , . . 0,1010 Analysis 3. , . . 0,1025 Analysis 4 . . . . 0.1035 Sample No. 2. Analysis 1 . . . . Analysis 2. . . . Analysis 3. . . . Analysis 4 . . . . Sample N o . 3. Analysis 1. . . . Analysis 2. . . . Analysis 3. . . . Analysis 4.. . .
Loss in weight. 0.1845
......
Lbs. coating per mile of wire. 4.81 ' 4.75 4.79 4.86
42.7 42.6 42.8
Lbs. coating per mile of wire. 8.55 8.54 8.52 8.56
Lbs. coating per ton of wire. 55.23 55.17 55.04 55.29
24.8 24.6 24.7
4.93 4.96 4.92 4.94
31.85 32,04 31.78 31.91
cc. KICrOl used.
0.1050
......
......
Lbs. coating per ton of wire. 31.07 30.68 30,94 31.39
DETERMINATION O F IRON I N ALLOY O F COATIKG.
The iron which is in combination with zinc in the coating as a n 'iron-zinc alloy will pass into solution as iron acetate and can be determined as follows: the combined lead acetate employed for the sample, together with the wash waters from the metallic lead, is heated t o boiling and the lead precipitated with a slight excess of sulphuric acid, the iron oxidized with nitric acid, and precipitated with ammonia, washed and weighed as iron oxide. Or if no balance be available, it may be washed, re-dissolved in sulphuric acid, reduced with zinc, and titrated with standard potassium permanganate solution. An idea of the amount of iron in the different kinds of zinccoated iron may be obtained b y the following results obtained from products found in the open market.
4
Iron in coating, Kind of material. Per cent. Ordinary hot dipped sheet. ....................... 2.26 Sherardized plate.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 ,70 Wet galvanized (electro deposited) sheet. . . . . . . . . . . . trace Wet galvanized (electro deposited) sheet. . . . . . . . . . . 7 46 NOTES.
( I ) I n order to insure the absence of free acetic
acid, and t o eliminate any danger of the iron base being attacked, enough lead oxide is added to render the resultant solution slightly basic. (2) It is important to immerse the test specimen for periods not shorter than three minutes a t a time. Otherwise a coherent deposit of lead may be formed.
April, 1911
(3) I n the case of articles t h a t are weathered, or have been subjected t o corrosion, i t is necessary first t o remove the layer of zinc salts from the surface by immersion in dilute hydrochloric acid. I n such cases the gravimetric determination b y difference must needs be used t o obtain accurate results. (4) I n washing the metallic lead free from lead acetate, i t is necessary in very a.ccurate work to use water previously boiled to free it from oxygen and carbon dioxide. (5) I n order to obtain exact lengths of wire, it is well t o cut the specimen a little longer than desired and file t o exact measurement. (6) The presence of a deep red color in the lead acetate after a test must not be taken as indicating a large amount of iron. Traces of iron as basic ferric acetate produce a strong color. ( 7 ) If the iron is determined b y titration with potassium permanganate, i t is necessary t o first remove it from the acetic acid, as with acetic acid potassium permanganate titration is not accurate. (8) The size of the specimen which can be taken, if the volumetric method be used, is limited b y the amount of potassium chromate solution required for reacting with the precipitated lead. Three inches of wire are all t h a t are necessary, except that greater accuracy in measuring is obtained b y using a longer piece. ( 9 ) Even when employed in the same way in which the Preece Test is used, the lead acetate solution has important advantages over copper sulphate in this: t h a t a bright copper surface on the zinc cannot be distinguished from the bright surface on the iron base. I n the lead acetate solution, bright adherent lead may be precipitated, b u t cannot be mistaken for the bright iron. Hence, if i t is desired to make a rough test for uniformity of coating on a wire, one-minute dips may be employed, and the uniformity with which the bright iron appears indicates the evenness of the coating. THE FORMATION TEMPERATURE OF CARBORUNDUM. B y HORACEW. GILLETT.
Received hlarch 1. 1911.
The temperature a t which carborundum is formed has been given in the literature a t values varying from 1200' C. to 3 8 7 0 ~C.I The only values on which any degree of dependence can be placed are those of Tucker and Lampen' who give for the formation of carborundum 195oO, and of graphite from carborundum, 2220' C. Some experiments having indicated t h a t carborundum was formed a t a lower temperature led t o an investigation of the point. The furnace used in the final runs was about 2 7 1 Stansfield, The Electric Furnace, 1907, 152 ; Acheson, Electrochem. I n d . . 1, 332 (1903); U. S. Pat., 723,631;Dunlap, Electrical Rariew, 62, 702 (1903);Scott, Jahrbuch d . Electrochemie, 12, [23 734 (1903); J . SOC. Chem. I n d . , 24, 501 (1903);Proc. Faraday SOC., April 4, 1905;Kunz, T r a n s . 7 , 249 (1905);Pring, J . Chem. Soc.. 93, 2104 (1908); A m . Electrochem. SOC., Greenwood, I b i d . , 93, 1483 (1908); Pring and Fielding, Ibid., 95, 1501 (1909);D z c f . Chem. IMef. ,Material, 1909, 19; Tucker and Lampen, J . A m . Chem. Soc., 28. 853 (1906).
= LOC. Cit.
G I L L E T T O N F O R - W A T I O S T E M P E R A T U R E OF C A R B O R U N D U M . inches long and 16 inches in diameter, being built up of fire brick in about the shape of the present commercial furnace.’ This held about I j o lbs. of charge and took up to j o I
