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Chemistry. ''llic dction oj' (■onccnlnili'd suIjtJnn'ic dcid on (jIiicpvoI 



I'sfeis of satniuitt'il monolxisii- jKttji acids.'' Pi-eliiiiijiaiT (.'oni- 

 mnnication. V>y B. W. van Eldik Thiemk. (Communicated by 

 Prof. S. A. Hoogewerff). 



As is well known, the sapoiiitieations may genei-ally be represent- 

 ed by the equation : 



RCOOR, 4 H,()^RCO()H + K,()H ....(]) 



that is we shall always obtain an equilibrium between the reacting 

 molecules which is dependent on the temperature, on the medium 

 and on the nature of the ester. 



The velocity of the saponitication is moreover very low and is 

 vigorously accelerated by hydrogen ions ; so long, liowe\'er, as the 

 quantity of the acid added does not considerably modify the natui'e 

 of the medium the equilibrium will not be changed thereby. 



In the technics of fat-saponitication dilute sulphuric acid is used as 

 catalyst, for instance in the Twitchell process ; from the above it 

 follows that we must not expect the process to conqjlete its course ; 

 it is considered satisfactory when the fat is resolved to 94 a 96"/„ 

 of free fatty acids. 



If we use a stronger acid the process becomes modified. Firstly, 

 we are dealing with another medium (in practice where the quantity 

 of acid is small the medium itself is changeable daring the process), 

 secondl} we have besides the first process also the following : 



RCOORi + H.,Ö0, ;± RCOOH + R^OSOjH . . . (2) 



which means the expulsion of one of the acid residues by the other 

 one. 



Here also, however, we may expect the reaction to be reversible 

 so that it will be completely to the right only when : 



a. The sulphuric acid added, is anhydrous (lOOYo), 



b. An excess of acid is added to dry fat, 



c. The temperature at which the action takes place, is kept within 

 definite limits. From this it follows, that the statement of Bünte ^) 

 that butterfat is completely saponified by sulphuric acid of sp. gr. 

 1.8355 (corresponding with 93.5°/u of H,SO^,) cannot possibly be 

 correct. 5 grams of butterfat are heated in an Erlenmeijer flask of 

 one litre capacity to 1Ü0\ 10 cc. of 93.5 7o sulphuric acid are 

 added and the whole heated for 10 minutes in a waterbath at 

 30 — 32'. 150 c.c. of Welter are added next. 



1) Ghem. Zelt. N". 12 1894 pg. 201, also Kreis Chem. Zeit. N". 76 1892 pg. 1394'. 



