November 14, 1919] 



SCIENCE 



465 



that explosives are necessarily connected with mat- 

 ters of a military nature and attempts to furnish 

 a general knowledge of the modern condition of 

 the industry for the busy man who would like such 

 a general idea of it, but does not find time to re- 

 view lengthy publications. Subjects discussed are 

 black blasting powder, straight dynamites and 

 gelatin dynamites, non-freezing straight dynamites 

 and gelatin dynamites, ammonia or extra dynamites 

 and gelatin dynamites, permissibles, miscellaneous 

 dynamites and non-freezing dynamites. Strength 

 bases are shown and strength comparisons be- 

 tween commercial dynamites and some important 

 military explosives are given. Developments on 

 lowering the freezing point of nitroglycerine are 

 discussed. Mention is made of various matters re- 

 quiring chemical or physical control in explosive 

 manufacture and the necessity is shown for such 

 control from the initial preparation of ingredients 

 to the final results of the blast. 

 J Chemicals received by the Bureau of Chemistry 

 during the war: H. E. Buc. During the last four 

 years about 1,300 shipments of chemicals from a 

 large number of dealers and manufacturers have 

 been tested in the Bureau of Chemistry. The 

 greater part of the reagents bore an analysis on 

 the label. Most of the chemicals examined are 

 satisfactory. Occasional impurities are found 

 often enough in chemicals from practically all man- 

 ufacturers to make it necessary to test all ship- 

 ments. 



Seport on the production of synthetic organic 

 chemicals in the Research Laboratory of East- 

 man Kodak Co., 1918 and 1919: C. E. K. Mees. 



SYMPOSIUM ON EEFBACTORIES, A. V. BLEININGER, 

 CHAIRMAN 



The classification of refractories: G. H. Brown, 

 Worlc of the Technical Department of the Be 

 frdctories Manufacturers' Association: R. M, 

 Howe. The Eef raetories Manufacturers ' Associa- 

 tion has maintained a central refractories labora- 

 tory for over two years. This laboratory is lo 

 eated at the Mellon Institute of Industrial Ee 

 search of the University of Pittsburgh and serves 

 annually over fifty refractories companies. Small 

 charges are made for the work done and this in- 

 come makes the system practically self-supporting. 

 The problems investigated are divided into two 

 classes, viz., general and specific. The general 

 problems are not discussed, but the specific prob- 

 lems encountered at different plants are consid- 

 ered briefly. These problems are met with from 

 the time of purchasing a site until the shipment of 



each load of brick. The owners must know the 

 extensiveness of a deposit before opening it up at 

 a large expense. The miners must have abundant 

 advance information concerning the physical prop- 

 erties of the different clays on the property: they 

 must be able to reject or accept different clays by 

 their hardness, color, structure, size of grain and 

 location. The securing of such data requires the 

 expenditure of considerable money, yet it seems to 

 be justified due to the economical selection of 

 .clays, the production of a uniform product, and 

 the avoidance of unjustified construction. The 

 clays, after beting mined, are used separately, or 

 mixed with bond clays to secure strength ; flint 

 clay to increase the refractoriness and resistance 

 to spalling; alumina to increase refractoriness; 

 silica to decrease the tendency to spall and shrink, 

 and grog for several reasons. After the mixes are 

 fixed, they are worked with water. This is some- 

 times considered a minor step, but it is now es- 

 tablished that the amount of water used in temper- 

 ing plays an important part in determining the 

 final structure of the brick. There is always one 

 definite proportion which is most suited to the 

 production of the densest brick. The time used in 

 working clay also enacts an important role in de- 

 termining the final structure a variation in 

 strength amounting to 25 per cent, of the total 

 having been observed when the time was varied. 

 Draw trial curves, which illustrate the behavior of 

 playa at different temperatures, are proving to be 

 of value. They not only tell the manufacturer how 

 Jiis clays must be worked but inform the con- 

 sumers how the bricks will behave in service. 

 Other factors which concern the process of manu- 

 facture are too complicated to report but they can 

 be and are being studied constantly. 



The selection of refractories for industrial fur- 

 naces: W. F. EoCHOW. Economy in the use of 

 refractories is governed by the selection of the 

 class of material best suited for the purpose, the 

 quality of the brick used and the design of the 

 furnace. Thermal insulation is made practicable 

 under severe temperature conditions by the use of 

 gUioa brick because of their good mechanical 

 strength at high temperatures. On burning, silica 

 brick undergoes partial inversions from quartzite 

 ^to cristobalite and tridymite. These inversions are 

 9,ccompanied by permanent volume increases. Ee- 

 cently it has been suggested that the lowering of 

 the specific gravity of silica brick on changing 

 from quartzite to the other crystalline forms, be 

 used as a measure of the extent of this transfor- 

 mation and that well-burned brick should have a 



