812 



THE INDIA RUBBER WORLD 



lordia lalifolia, is thinned and used for proofing balloon fabrics, 

 gas helmets, etc. The balloon fabric is composed of two sheets 

 of thin flexible material, one or both sheets being of absorbent 

 material. One of the sheets has applied to its outer surface a 

 coating of rubber or waterproof varnish, and to its inner sur- 

 face a thin layer of birdlime. The other sheet has a coating of 

 rubber, etc., on the surface next to the birdlime, the other surface 

 being left bare. (C. A. Cleghorn, Brackenside, Woburn Sands, 

 Bedfordshire, and Gayner Pneumatic Co., 95 Cannon street, Lon- 

 don. British patent No. 142,160.) 



A Tire Filling Molhed in Cylindrical Form and Used to 

 replace the ordinary inflated inner tube is formed by add- 

 ing sulphur chloride (six pounds, nine ounces) to a mixture of 

 soya bean oil (25% pounds), magnesia (two pounds), and 

 Venetian red (five ounces). The oil is cooled before admixture. 

 to 20-32 degrees F. to moderate the reaction. To insure uniform 

 cooHng the molds are provided with tubular metal cores which 

 are withdrawn when the composition has set and the central 

 space is filled with a fresh quantity of composition. (W. G. 

 Wright, 1838 Collingwood street, Vancouver. B. C, Canada. 

 British patent No. 142,416.) 



PROCESS OF MAKING H EXAM ETHYLENE TETRAMINE. 



Commercial ammonium carbonate is dissolved in 40 per cent 

 formaldehyde solution, the reaction taking place readily without 

 application of heat and with brisk evolution of carbon dioxide. 

 The solution is evaporated to dryness on a water bath under 

 reduced pressure, and the residue is sublimed in vacuo or re- 

 crystallized from absolute alcohqj. To compensate for its var- 

 iable composition the amount of ammonium carbonate taken 

 should be about 10 per cent in excess of the theoretical quantity. 

 The yield of hexamethylene tetramine is about 66 per cent of the 

 theoretical amount. (W. Herzog, "Zeitschrift Chemie," 1920, 

 33, 48.) 



LABORATORY APPARATUS. 



THE SCHAAR UNIVERSAL ELECTRIC HEATER. 



THE ILLUSTRATION shows an all-purpose electric heater that can 

 IS) be used as a hot-plate or for heating flasks 



or test tubes. As a flask heater it displaces 

 the usual tripod or support and burner. Test 

 Wibes are heated by placing them in the per- 

 forated cylinder which fits into the center of 

 the heater between the coils. 



To transform the heater into a hot-plate 

 the conical top is removed and replaced with 

 a metal disc which fits over the opening. 

 The heater is mounted on a solid base 

 which can be screwed to the table. (Schaar 

 & Co.. .S56 West Jackson Boulevard, Chicago, 

 Eleituil- He.ster. Illinois.) 



SPECIFIC GRAVITY CHAINOMATIC BALANCE. 



Reference to the illustration shows the general construction 

 of this balance, advantage having been taken of the salient features 

 of the analytical chainomatic balance, which has so revolutionized 

 weighing in analytical chemistry. There are no loose weights to 

 use, all weighings or determinations are accomplished by placing 

 the sHding weight in the proper notch on the beam, and obtain- 

 ing the final reading by adding weight to the beam by means of 

 the chain. 



The balance is furnished either with or without a case. In 

 the former instance it has a sensitivity of one-tenth of a milli- 

 gram. The instrument has an aluminum beam, agate bearings, 

 glass base, spirit level, etc. The plummet displaces exactly two 

 grams of distilled water at 15 degrees C. The enclosed ther- 



SrECTFic Gravity Balance Without Case. 



small quantities of liquid are available. (Christian Becker, In- 

 corporated, 92 Reade street. New York.) 



MONOCHROMATIC FLAME ATTACHMENT AND TUBE SUPPORT. 



A new moiiochromalic Hame attachment adaptable to any 

 ordinary Bunsen burner is shown ia 

 the accompanying illustration. It 

 consists of a simple cup arrangement 

 permitting the solution of any salt 

 to be used. 



venient and simple stand 

 or support for tubes is 

 here shown. It is com- 

 pact, low priced and 

 suitable for supporting 

 tubes of any kind and 

 in connection with hold- 

 ing apparatus in place. 

 Both of these useful 

 laboratory accessories, 

 are marketed by the 

 same company. (Cen- 

 tral Scientific Co., 460 

 East Ohio street, Chi- 

 cago, Illinois.) 



Flame 

 Attachment. 



FINENESS AND TEXTURE OF PIGMENTS. 



An unique method for testing the fineness and texture of pig- 

 ments is given by H. A. Gardner in Circular No. 50 issued by 

 th^ Paint Manufacturers' Association of the United States 

 (Philadelphia). 



The method of test consists in rubbing with the finger a por- 

 tion of the pigment across the grooves of an Edison disk phono- 

 graph record and observing the surface under a microscope. 

 There are 150 grooves per inch of radius on a disk record, and 

 each groove has a radius of curvature of 0.004-inch and average 

 depth of 0.001-inch. The feel of the pigment on the record 

 under the finger, together with the microscopic examination, will 

 show characteristic difi^erences in the pigments. The number of 

 particles per unit weight of pigment may be determined with a 

 haemacytomeler u.sing a suspension of one gram of pigment in 

 one liter of water containing a small amount of gelatin. 



