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gion under study is described. “ Chapter I V includes the general study of the chemic and lithologic characteristics and the correlation of the Georgia granitic rocks.” T h e general principles of rock-weathering are discussed in Chapter V, and in the concluding Chapter V I are grouped tables of statistics, physical tests, and analyses by the author, the last giving the more important constituents without differentiation of the oxides of iron. For brief statements of many of the points brought out and elaborated in the discussions, the reader is referred to abstracts, in this journal, of preliminary papers by the same author that have appeared within the past two years (this Journal, 23, R 129,24, R 120, W. F. HILLEBRAND. 123) 342’ 3%).
ANALYTICAL CHEMISTRY. Report on a Cooperative Chemical Analysis of a Copper Slag. BY THORN SMITH. Eng. Mi%.J . , 75, 295-2g7.--The wide differences in the results obtained by twenty-three analysts on a sample of copper slag are accounted for as follows : Silica.-Low results are due to the fact that a second evaporation of the filtrate was not made. High results indicate that the silica should be examined for impurities or that heating during ignition was insufficient. Iron.-The errors in the determination of the iron are due to the lack of an accurate standard substance for determining the strength of the permanganate or dichromate solutions. Alumina. -The low results were nearly all obtained by the phosphate method. T h e high results, usually obtained by difference, were due to silica either from the original substance or from t h e glassware. Lime.-High results were due to insufficient washing before titrating with permanganate. Low results are caused by too much washing with hot water or by filtration before precipitation is complete. Magnesia. -High results are due to insufficient washing, the presence of silica or to too low temperature during ignition. Low results are due to incomplete precipitation or to too little ammonia i n the solution. Zinc.-The “ Low method ” for zinc is not to be recommended i n the presence of manganese and much iron. A majority of the analysts used the ferrocyanide method and the chief source of error was probably in standardizing the ferrocyanide solution. .kfanganese. -‘ ‘Volhard’s method’ ’ was generally used. Analysts are advised to examine the zinc oxide and sodium carbonate for manganese, Copper. -The cyanide and iodide methods give varying results on account of incomplete precipitation on the zinc or aluminum, and oxidation and solution during the washing. Weighing as
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oxide may give high results through the introduction of other bases. Su&hur.-Oxidation with nitric acid and potassium chlorate followed by precipitation as barium sulphate gave fairly satisfactory results. B. S. CUSHJIAS.
Smoke and the Determination of its Density. BY A . A. CARI’. Elect. World and Ezg., 41, 7 j2.-1n making smoke density determinations, observations of the condition of the smoke should be made a t frequent and equal intervals as, for instance, every half-minute. T h e observations are best made by the use of a smoke chart consisting of five rectangles printed in different shades, namely, light gray, darker gray, very dark gray, light black, and intense black. When the test is important, not less than two separated observers should make their records, rioting time and number expressing the shade of smoke existing at t h e time, and these records should be compared. Besides these observations some one in the boiler room should note the time of each firing and cleaning, and also state the conditions existing at other recorded times, as “forcing the boiler,” “ running light,” etc. If furnace gas analyses are made during these observations, and all of these results are compared on cross-section paper, a careful analysis of existing conditions pertaining to the production of smoke in the plant under consideration may be made, and a means for further suppressing the smoke can generally be found by making the proper deductions. It is convenient to use a timekeeping apparatus in making the smoke observations. A machine which has been used consists of a cylirider around which is a paper for the record, and which is turned by clock-work. X given distance around its circumference represents one minute. ’The pencil, pressing against this paper on the drum is moved across the face of the cylinder (parallel to its axis) by the observer, who pulls the slide rod carrying the pencil to its extreme left position when there is “no smoke.” When the pencil is not moved, the revolving of the drum causes it to draw a line around the drum. For “slight smoke” the observer pulls the pencil over one division to the right. for “medium smoke” another, another for “black smoke,” and again another for “very dense This gives the observations plotted, the ordinates repsmoke. resenting time, and the abscissae degrees of smoke. One improvement by the author makes more accurate and convenient the movement of the pencil by the operator, and another decreases the size of the recorder and permits of using a long roll of cross-section paper. BENTONDALES. The Use of the Zinc Reductor in the Estimation of Vanadic Acid. BY F. A. GOOCHA N D R. D. GILBERT. A m e r . j . Sci. (4). 15, 389-392.--The reduction of vanadic acid by zinc and acid yields an irregular product approximating the dioxide in I ’
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composition. To convert this into the more stable tetroxide before the titration with permanganate, the authors tried subjecting it to the action of air a t various temperatures and for various lengths of time. Their titrations are made, after heating to 80°, with nearly twentieth-normal potassium permanganate solution, standardized by reference to twentieth-normal arsenious oxide. Blank experiments show that a correction of 0.2 cc. of permanganate solution has to be subtracted, because the " reading color " does not develop in the acid solution until this amount has been added. Their figures show that, although the oxidation by air appears to proceed rapidly at first, the complete conversion of the lower oxides to tetroxide by such action takes place with too great slowness and uncertainty to form the basis of a reliable and rapid quantitative method. T h e authors find then that silver oxide and silver salts, especially silver sulphate, will cause this oxidation, and not oxidize the tetroxide to pentoxide. I n these experiments the flask which is to receive the solution from the reductor is charged with a saturated solution of silver sulphate in varying amounts. LVhen the reduced solution from the reductor meets the silver sulphate a muddy deposition of finely divided silver begins, but upon boiling the mixture, the silver collects into a single spongy mass, which has to be filtered out only because of the action of the permanganate upon it. T h e solution is heated again to the boiling-point and titrated with twentiethnormal permanganate. For the smaller amounts of vanadium (0.0767 gram V,06) the error in the given results varies from 0.13 per cent. to 0.65 *pet cent. For a larger amount (0.1918 gram V,O,) the errors in two determinations given are 0.78 per cent. and 1 . 2 5 per cent. T h e wider variations in these two are probably due, according to the authors, to the difficulty of catching t h e pink end reaction in presence of the reddish yellow color which appears as the vanadic acid is formed in considerable amount. But this is a difficulty inherent in the permanganate process of titration when large amounts of V,O, are involved. BENTONDALES.
The Use of a Rotating Cathode in the Electrolytic Determination of the Iletals. BY F. A. GOOCHAND H. E. MEDWAY. Ante),. 1.Sa'.[4], 15,320-323.-The cathode consists simply of a 20 cc. platinum crucible which can be rotated 600 to 800 times per minute. I t is held by means of a rubber stopper on the end of the vertically placed shaft of a small electric motor. Connection between the crucible and the shaft is secured by soldering a narrow strip of platinum to the shaft and bending it upwards along the outside of the stopper, T h e shaft is made in two parts. T h e electrolyses are conducted in glass beakers with platinum plate anodes. T h e iiegative pole of the battery used as the source of the current is connected with the bearing in which the shaft
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rotates, and the positive pole with the platinum plate. A series of electrolyses of a solution of copper sulphate acidulated with dilute sulphuric acid is given, in which the current varies from 2 . 7 to 13.3 amperes per square decimeter, the time from ten to twentyfive minutes, and the error from 0.0 to nearly 0.5 per cent. in one determination (0.0003 gram in 0.06 j1 grain taken). Other series, equally as good, are given showing the results of the electrolysis of proper silver and nickel salt solutions and differently acidulated, copper salt solutions. Other metals are said to behave similarly. T h e deposits are sufficiently coherent and compact to permit accurate manipulation and weighing. T h e advantages of the process are the rapidity with which it can be carried out, its exactness and its simplicity. BERTOXDALES.
Photometer Attachment. Elect. IVodd a d Eng., 41,6 j0.This is a simple angulating device, designed by the Shelby Electric Company, which fits into the socket of any standard photometer. I t enables one to turn the lamp so as to determine not only the horizontal candle-power, but to measure the light from any desired angle. Most disinterested authorities strongly favor the determination of the real value of an incandescent lamp by obtaining its spherical candle-power and coilsidering this with the actual current required to operate i t , in preference to measuring t h e lamp in the arbitrary manner generally used at present, namely, for its horizontal intensity. The principal argument against rating lamps by their spherical candle-pon-er has been that there was no instrument by which such measurements could be taken at one reading that was not extremely complicated, and therefore not adapted to commercial use. Illuniiiiatioii is divided into t n o classes, general and local. The \ d u e of a lamp for general illumination can only be determined by considering the light emitted in all directions, while by far the greater part of the light used in local illuniination is delivered through the end of the lamp opposite the base or within 45' therefrom. Hence it is unfair t o rate the lamp solely by the light delivered horizontally. BENTOX DALES.
I.,
The Simmance-Abady Photometer. A m e r . Gas Lzght 78, 53o.-If the rays from two sources of light, one being, for example, red, the other green, are allowed to fall in rapid succession upon a screen or directly upon the retina, the eye ceases to distinguish the colors and is sensible only to the degree of intensity of the illumination. It1 this photometer, beams from each source of light are directed on a paper screen, across which vibrates a shutter, cutting off each ray in turn. If the lights are unequal in power the oscillation of the shutter at a given speed produces a vibrating effect, h u t on moving the screen and shutter nearer the weaker light, a point is reached where the rays from the two sources are equal, this being indicated on the screen by a total
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absence of vibration. T h e introduction of this practical form of photometer has enabled very accurate determinations to be made of the actual power of electric arc lamps and of the Welsbach light. T h e delicacy and accuracy of the readings of this instrument are shown by the facts that when lights of the same color are tested by it, the results agree exactly with those obtained with the Bunsen or the Lummer-Brodhun apparatus ; and that when the lights vary in color, different operators, although they disagree totally in their readings with these instruments, obtain results that coincide very closely when the same lights are tried with the Simmance-Abady instrument. BENTONDALES.
Modification of Nessler’s Tube. BY HERBERT J. WATSON. A m . ]ouYn. Pharm., 75, 166.-The jar (which is illustrated in a cut accompanying the original article) is 12 inches in length, 3/4 inch in diameter, 9 inches from base to top mark ( 5 0 cc.) and graduated in 5 cc. with dashes for the I cc. graduations. A small tube projects from the side at the base, which may be plain or have a stop-cock. A number of plain tubes ( 5 0 cc. graduation) are necessary to collect the distilled ammonia. T h e method consists in connecting the side tube with a burette by a small rubber tube. T h e three tubes, each of free and of albuminoid ammonia, are nesslerized and mixed together. One of these tubes is placed beside the one connected with the burette containing the standard ammonia solution and moved with a vertical movement. T h e liquid in the standard column is made to increase or decrease at will and the number of cubic centimeters is always visible. T h e jars with the side neck cost $ 1 . 7 5 , and with stop-cock, $2.50. J. 0. SCHLOTTERBECK. Il ETA LLURG ICA L C H EIl ISTRY. Newfoundland Ilining in 1902. Eng. Min. J., February 14, 1903.-Figures furnished by J . P. Hawley, head of the department of mines, show 728,721 tons of iron ore mined, valued at $I per ton ; 71,482 tons of copper ore, valued at $3.50 per ton, and 26,000 tons of pyrites, valued at $4.50 per ton. Half the iron ore was worked at Sydney, Nova Scotia. Deposits of manganese ore covering a large area, and assaying from 35 to 41 ‘I, per cent. manganese, exist in Conception Bay. J. W . RICHARDS. The Concentration of Ores by Oil. BY W. MCDERMOTT. Eng. Mzn. /. February 14 and 21, 1go3.-F. E. Elmore has developed a practical and economical method of utilizing the remarkable power of some oils to absorb certain minerals and metals. I t is entirely a surface action a s between the oil and the wet particles of mineral, and the result is that the particles enter into the body of the oil. T h e essential points are ( I j the nature
