August 22, 1902.] 



SCIENCE. 



289 



siders that his results bear very strongly in 

 favor of the theory that the rancidity of 

 fats is brought about (primarily, at least) 

 by the influence of the growth of micro- 

 organisms, or the enzymes produced 

 thereby. 



On Carbyl Salts : M. Gomberg. 



The paper dealt with results obtained, 

 proving beyond doubt that certain organic 

 halogen compounds must be considered as 

 salts, from the chemical as well as the phys- 

 ical point of view, being strong electrolytes. 

 The theory of dissociation can therefore be 

 applied to substances other than those 

 which have been classed as acids, bases and 

 salts. 



Some Preliminary Expervinents upon the 

 . Clinkering of Portland Cements: B. D. 



Campbell. 



In the first part of the paper the author 

 describes the method used in preparing a 

 number, of mixtures of marl and clay or 

 shale. These mixtures were burned in a 

 rotary cement kiln, a description of which 

 appeared in the Journal of the American 

 Chemical Society, Vol. 24, No. 3, p. 248. 

 During each burxiing a series of sam- 

 ples of clinker was collected at tem- 

 peratures differing by 22° to 30°. Tests 

 of the time of setting and the behavior of 

 the pats, after keeping twenty-four hours 

 in boiling water, were made on each 

 sample of clinker collected. The details 

 of the influence of the temperature of 

 burning on the pats from each series are 

 given in seventeen tables ; all the results are 

 summarized in one large table, and com- 

 pared with those of A. Meyer {Thonin- 

 dustrie Zeitung, Vol. 73, p. 1201). The 

 author has summarized the preliminary 

 work as follows : 



Viewed from the standpoint of the in- 

 fluence of chemical composition upon the 

 changes in temperature necessary to pro- 



duce a sound cement, and the temperature 

 at which the clinker mil give trouble by 

 sticking in the rotary, we find to be : The 

 minimum temperature necessary to pro- 

 duce Portland cement which will give a 

 perfect pat test from fresh clinker is about 

 1450° C. This temperature is for mini- 

 mum amount of CaO. It increases with 

 increase of CaO, until in ordinary commer- 

 cial cements it reaches 1550°. With the 

 most heavily limed commercial cements this 

 figure woiild be somewhat higher. It de- 

 pends somewhat on the length of time 

 required to pass through the rotary, slow 

 driving tending to lower the temperature. 

 The substitution of AUOj or FCoOa for 

 SiO,, that is, the use of a richer clay, lowers 

 the over-burning temperature, but may 

 lower or raise the temperature required for 

 perfect hot test. With mixtures high in 

 CaO, the burning temperature for perfect 

 hot test is lowered by this substitution, but 

 with mixtures high in CaO, the burning 

 temperature required for perfect hot test is 

 raised and may become coincident with the 

 overburning temperature. Any attempt to 

 raise the over-burning temperature by in- 

 creasing the proportion of lime will fail 

 to give a perfect hot test, even at the over- 

 burning temperature. This is a confirma- 

 tion of what manufacturing experience has 

 shown, that with lean clays heavily limed 

 there is a margin between the proper clink- 

 ering temperature and the over-burning 

 temperature, while with rich clays, in order 

 to prevent the clinker from balling up 

 great care must be exercised to maintaii; 

 the proper clinkering temperature. ^With 

 the amount of CaO found in ordinary ce- 

 ment the introduction of eight or nine per 

 cent, of magnesium oxide has but little 

 influence on the temperature for perfect 

 hot test or over-burning temperature. So 

 far as the clinker is concerned, magnesium, 

 as has been maintained by Newberry, acts 

 as an inei-t substance. 



