November 



1906.] 



THE INDIA RUBBER WORLD 



39 



THE USE OF MAGNESIA WITH RUBBER COMPOUNDS. 



By Werner Escli, Ph. D. 



TO Tins EnrroR oi- Tin-: India Ruhukr Wokli> : The kinds of the calcined Magnesia have in dry state a very dif- 



issue of your journal of Septemljer 1 mentioned (on ferent volume, but do in fact possess quite the same specific 



page 389) the use of Magnesia with India-rubber gravity (which must be determined under parafEne oil, be- 



compounds. (.specially taking notice of some recent cause water has a chemical action on Magnesia, producing 



papers of Dr. Ditinar. I find that a serious mistake has been hj-drate of Magnesia) it may be pointed out that a ball and a 



made bj' your correspondent, for he speaks of light carbonate hollow cylinder, which may have quite the same volume and 



of Magnesia, while the papers of Dr. Ditmar dealt with replace both quite the same quantity of oil or other liquids, 



heavy calcined Magnesia and light calcined Magnesia, both in a dry accumulation in measuring cylinder tubes will show 



of them being in a chemical sense oxide of Magnesia. Your (|uite a diflerent " apparent volume ". 



correspondent in fact confounds calcined Magnesia with By the special structure of the light calcined Magnesia 

 carbonate of Magnesia. The difference of the contents of 100 grams of this material show a volume of 763 cubic cen- 

 pure oxide of Magnesium (Mg O) in both of the technically timeters by dry introduction into a graduated tube for meas- 

 used Magnesia products is very important, carbonate of uring, against 141 cubic centimeters with heavy calcined 

 Magnesia containing between 40 to 45 per cent, of Mg O. Magnesia under the same conditions. Then may be intro- 

 whileo.xide of Magnesium contains 96 to 98 per cent. Mg O. duced into each of the same graduated tubes 100 cubic centi- 

 Only the latter is used as an accelerator of the vulcaniza- meters of heavy mineral oil, and the tubes may be slowly 

 tion, carbonate of Magnesia only being a filler and having heated uutil all air bladders have disappeared : after cool - 

 nearly the same effect together with rubber compounds as iug, the tube containing heavy calcined Magnesia will show 

 whiting has. 127 to 129 cubic centimeters, and the tube containing light 

 It is ^a scarcely known fact that Chailes Goodyear, the calcined Magne.sia 129 to 131 cubic centimeters; that is to 

 pioneer of the vulcanized rubber industrj-, already has made say : the specific gravity of both kinds of calcined Magnesia 

 use of calcined Magnesia in several of his rubber compounds, are practically identical. The same conditions take place, if 

 The use of calcined Magnesia has been confined for a long both kinds of calcined Magnesia are mixed with India-rubber, 

 time to only a few rubber comjiounds, but, by the remark- If one kilogram of heavy calcined Magnesia is introduced 

 able development of the rubber trade, especiall}' the tire in- into a rubber compound, only 1 100 cubic centimeters of air 

 dustry, the industry of open steam cured goods, and the bladders must be driven out, while in introducing one kilo- 

 manufacture of rubber insulated cables, etc., the use of cal- gram of light calcined Magnesia into a rubber compound, 

 cined Magnesia has highly increased. Most of the big rub- one has to dri\e out the high amount of 7300 cubic centi- 

 ber factories in Europe and America can not do without meters. This comparison shows the superiority of heavy 

 this highlj' appreciated chemical. The vulcanization — i.e., calcined Magnesia evidently. 



"addition " of sulphur to India-rubber, in chemical mean- Comparative experiments on the acceleration of the vul- 



ing — can easily be accelerated by appropriate additions of cani/.ation by additions of different kinds of Magnesia have 



calcined Magnesia to the compound in question. Such an thoroughly proved that the heavy calcined Magnesia (special 



addition is often inevitable especially together with pitch rubber quality Lehmann & Voss brand) has a higher effi- 



like or soft rubbers in open steam cured compounds. All ciencj' relating to the acceleration of the vulcanization than 



rubbers with a high amount of resins, such as Mexican any other brand of calcined Magnesia. 



Ouayule, Cameroon, Assam, Borneo, etc., usually give bet- Two corresponding compounds with additions of 20 per 



ter goods, if compounded with appropriate additions of cal- cent, calcined Magnesia gave the following coeflBcients of 



cined Magnesia ; but even the best Bolivian Parfi rubber vulcanization : [ Coefficient of vulcanization means the 



gets a better tenacit}', if compounded with calcined Magnesia amount of chemically combined sulphur which is calculated 



than without this accelerator of vulcanization. on 100 parts of pure rubber (free from resins, etc.)]; 



There exist two kinds of calcined Magnesia; the lieavy Heavy calcined Magnesia, Lipsia brand 4 99!^ 



,,,,■,, , • J IT 1 ;., J ■vr„ .;„ ;. „, Heavy calcined Magnesia, Lehmann ^^ Voss 5-42% 



and the light calcined. Heav}^ calcined Magnesia is pro- - <= r ^ 



. , .... 1. 1 r «» 1.- t. Corresponding compounds with additions ol 60 percent, 



duced by calcining heav\' carbonate of Magnesia, which ^, . ,,,, . ,.,..,, 



. . . r • ■,. t- r I. 4.111 • 1 *• of calcined Magnesia gave the following coefficients of vul- 



carbonate is won by precipitation of hot Magnesia solutions . . 



bv hot solutions of soda. The light calcined Magnesia is caniz . .,..,, 



" , , , ... ., ,. , ^ , ^ c -., , Heavy calcined Magnesia, Lipsia brand 3-9J% 



produced by calcining the light carbonate of Magnesia, and jj^^^^ calcined Magnesia. Lehmann & Voss 8.05% 



this light carbonate is the precipitation product of Magnesia Corresponding compounds of 100 reclaimed rubber, 50 cal- 



solution together with soda solutions, both carefully cooled, (^^-a^^ Magnesia.and 3 sulphur, gave the following coefficients 



The difference of both kinds of calcined Magnesia concerns of vulcanization ; 



onl}' the structure, so that light calcined Magnesia in a dry Heavy calcined Magnesia, Lipsia brand 6.91% 



state seems to have a very big volume, but if the air bladders "^avy calcined Magnesia. Lehmann cS: Voss 9 37% 



are driven away and the pores of the material filled by intio- F'"^">-' corresponding compounds of loo reclaimed rubber, 



ducing the light Magnesia into liquids, it is easilv to be seen ^o calcined Magnesia, and 7 sulphur, gave the following co- 



that the big volume cannot have the expected efi^ect. if light efficients of vulcanization ; 



, . , ,, -I 11.. n -.t T 1- 11 Heavy calcined Magnesia, Lipsia brand 5-71% 



calcined Magnesia is kneaded together with India-rubber on Light calcined Ma|ne.sia, Lipsia bran.l 5.76? 



the mixing rollers. Heavy calcined Magnesia, Lehmann & Voss 6.11J 



Only to give the reader an idea of the possibility, that both These experiments have been carried out by chemists who 



