INORGANIC ANALYSIS 261 APPARATUS, ETC. New Colorimeter. C. F. Sammet. (J. Ind. and Eng. Chem., 1916,8, 519-521.) -The instrument described and illustrated in this paper is designed especially for determining the colour of commercial turpentines, but may serve for other purposes- Turpentines are now graded according to the depth of liquid required to match a Lovibond No. 1 yellow glass. Direct comparison is difficult, and the usual practice is to take as the standard a 25 mm.depth of the turpentine in question and a No. 2 yellow glass, and to compare this with a No. 1 yellow glass superimposed on a deeper layer of turpentine, the depth being varied until a match is secured. The depth in mm. of this second column of turpentine, less 25, is the depth corresponding to 1 Lovibond unit, and serves to grade the turpentine.The manipulation required by this method is tedious, and the eyes get so tired before the final comparison is made that only roughly approximate matches are secured. The apparatus described and illustrated greatly simplifies the manipulation, and enables two observers to obtain closely concordant results. I t consists essentially of a horizontal metal cell, 300 mm.long, and a vertical eyepiece mounted on a travelling carriage above the cell, the travelling carriage also carrying two 45" prisms, back to back and immersed in the liquid in the cell. The cell has glass ends, and each end is illuminated by a 100 watt metallic filament lamp of frosted glass, screened by a sheet of 6 ' daylight " glass. When the illumination at the two ends of the cell is equal and the eyepiece and prisms exactly in their middle position, the field observed through the eyepiece should appear uniform, whatever the contents of the cell.The cell Is262 ABSTRACTS OF CHEMICAL PAPERS filled with a dark turpentine, and one of the lamps slightly shifted if necessary until the field appears quite uniform.A dark turpentine serves best for making this adjustment. The turpentine to be tested is now placed in the cell, a No. 1 yellow glass over one end of the cell, and a No, 2 yellow glass over the other end, and the carrier is moved towards the No. 2 glass until the field once more appears uniform. The difference between the distances from centre of the travelling carriage to the two ends of the cell gives the depth of turpentine corresponding to 1 Lovibond unit, and the carrier is provided with a pointer and the cell with a scale to enable these distances to be read off in mm.With this apparatus, two observers should never differ in their reports by more than 8 per cent., which is well within the limits required in grading turpentine. G. C. J. Lutes and Cements.S. S. Sadtler. (Chem. News, 1916,113,257-259.)--The following formulae are given for the preparation of cements likely to be of use in the laboratory. Water-proof.-Various mixtures of asphalt, a solvent, and a filler, are described. Mixtures of boiled linseed oil, clay, asbestos, and red or white lead, are water-proof, as is also a mixture of flaxseed meal and water. Portland cement mixed with water containing a small quantity of sodium silicate or glue makes a good lute.Oil-prooj.--(a) Glue, 2 ; glycerol, 1; water, 7, parts by weight. ( b ) Putty made of molasses and flour. (c) Glycerol, 90; water, 10, parts by volume ; litharge, 90 ; red lead, 10, parts by weight. id) Sodium silicate and whiting or barium suiphate. (e) Plaster of Paris and glue.Acid-proof.-(a) Many of the asphaltic mixtures are acid-proof. (b) Equal weights of rubber and boiled linseed oil, the rubber being first dissolved in carbon disulphide. (c) Rubber, 1 ; boiled linseed oil, 4 ; fire-clay, 6, parts by weight. (a) Rosin, 1 ; sulphur, 1 ; fire-clay, 2 parts, melted together. ( e ) Litharge, 80 ; red lead, 8 ; flock asbestos, 10 pounds, mixed with 6 quarts of boiled linseed oil.cf) Various mixtures of barium sulphate, powdered glass, china clay, casein, and sodium silicate. Chlorine Resistant.-Powdered glass, 1 ; Portland cement, 1 ; sodium silicate, 1. Marine Glue.-Crude rubber, 1 ; shellac, 2 ; pitch, 3, parts by weight, the rubber being first dissolved in carbon disulphide. Machinists' Cement.-Linseed oil, 6 ; rubber or guttapercha dissolved in carbon disulphide, 1 part, by weight ; after twenty four hours, red lead is added in quantity sufficient to make a stiff paste. Leather Cement.-(a) Equal weights of glue and American isinglass, softened in water and then boiled with the addition of tannin.(b) Guttapercha, 1 ; benzene 10; linseed oil varnish, 12, parts by weight. (c) Guttapercha, 8 ; pitch, 1; shellac 1; and olive oil, 1 ; melted together.Iron Cement.-Iron filings, 40 ; manganese dioxide or flowers of sulphur, 10 ; ammonium chloride, 1 ; Portland cement, 20 to 40 ; and water sufficient to form a paste. Crucible Cements.-Mixtures of clay and borax, or sodium silicate and powdered glass and sand, may be used for cementing lids on crucibles. Fire-clay is the best cement for graphite, whilst tar or pitch forms an all- carbon binder.d water-proof cement which will stand a high temperature consists of a mixture of fine sand and 10 per cent. magnesium chloride solution made into a stiff paste, and painted with sodium silicate solution after application. Magnesia Composition for FzLrnaces, etc.-Hard burnt magnesia, SO, and light burnt tnagnesia,APPARATUS, ETC.263 20 parts, made into a stiff paste with water, oxide and wood pulp or sand are mixed with magnesium chloride solution (18" B.). Oxychloride Ceme7zts.-Magnesium w. P. s. Simple Device for Regulating Pump Used in Exhausting a Vacuum Oven, G. P. Plaisance and D. V. Moses. (J. Amer. Chem. SOC., 1916, 38, 1063-1065.)- Since even the best vacuum ovens are not air-tight, it is usual to operate the pump L: Qrau Or b .r G A 5 continuously whilst the oven is in use; but, as the leakage is -P N -L M usually small, this is wasteful of power. The apparatus illustrated is intended to check this waste by cutting out the motor operating the pump when the vacuum is somewhat higher than is needed (say 20 mm. pressure, where an average of 40 mm. is desired), and switching on again whenever the vacuum falls below some approved minimum (e.g., a pressure of 60 mm.).A is the tube leading to the pump, and B a trap to catch any mercury that may be drawn out of D. D contains mercury into which tube E (80 cm. long by 6 mm. internal diameter) dips to a, depth of I cm. F and G contain calcium264 ABSTRACTS OF CHEMICAL PAPERS chloride to prevent water given off by contents of oven from contaminating mercury or oil in pump.H i s the oven. When the pump stops, mercury rises in E corre- sponding to the vacuum and closes the system. Vhen the pump runs, the air has only to bubble through 1 cm. of mercury. Attached to the oven on the other side is the U-tube K L containing mercury and supported by standard 0. K i s 90 cm.long, and has an enlargement, 1 ( 3 cm. in diameter), 80 cm. from bend of U. L is 80 cm. long by 1 2 mm. internal diameter. I t contains a glass float, H, 12 cm. long, with small bulb a t base and small projections at top to centre it. The rod N con- nects M to an ordinary throw switch, P, on porcelain back R. The switch is mounted on a block, S, which can be slid up or down the standard 0. The wireR T lead to the motor. When the desired vacuum is reached, block S is adjusted so that float M will just open switch. As air leaks into the oven, the column of mercury raises float and closes the switch, thus starting pump. The use of the bulb I reduces the pressure required to throw the switch to 25 mm. of mercury, in place of 80 mm., the height which would be required were the tube without the bulb. I n the authors’ experience with a Freas’ electrically heated oven connected to a Crowell’s pump, operated by a 1 horse-power motor, the device illustrated reduced the cons1 mption of electrical energy over 80 per cent., the motor running for periods of about thirty seconds at intervals of three minutes or less. G. C. J.