C.H^-OC,H, 



Mr. R. Mallet on Expansion by Refrigeration. 231 



showing that vanilline doas not contain more than one hydroxylic 

 group. 



The constitution of vanilline being thus made out, there could 

 be no doubt regarding the structure of the product of fermentation 

 from which vanilline arises. This compound is the ethylic ether of 

 vanilline, 



7 /0CH a 



\C O H. 



That such is the constitution of the body is proved by the simul- 

 taneous formation of ethylic aldehyde when vanilline is formed. 

 We obtained, however, an additional confirmation of this concep- 

 tion by submitting the product of fermentation to the action of 

 hydriodic acid under pressure, when an alcohol iodide was formed, 

 which we succeeded in separating into the iodides of methyl and 

 ethyl, 



/OCH 3 /OH 



C 6 H 3 fOC 2 H 5 + 2HI = CH3I + C 2 H 5 I + C 6 H 3 (-OH 

 \COH \COE 



The experiments we have described in this note were performed 

 in the laboratory of Professor A. W. Hofmann, to whom we are 

 deeply indebted for the advice and assistance he has given us in 

 the course of these researches. 



June 11, 1874. — The following communications were read :— 



" On the alleged Expansion in Yolume of various Substances in 

 passing by Refrigeration from the state of Liquid Fusion to that of 

 Solidification." By Robert Mallet, C.E., E.R.S. 



Since the time of Reaumur it has been stated, with very 

 various degrees of evidence, that certain metals expand in volume 

 at or near their points of consolidation from fusion. Bismuth, cast 

 iron, antimony, silver, copper, and gold are amongst the number, 

 and to these have recently been added certain iron furnace-slags. 

 Considerable physical interest attaches to this subject from the ana- 

 logy of the alleged facts to the well-known one that water expands 

 between 39° E. and 32°, at which it becomes ice ; and a more ex- 

 tended interest has been given to it quite recently by Messrs. 

 Nasmyth and Carpenter having made the supposed facts, more 

 especially those relative to cast iron and to slags, the foundation 

 of their peculiar theory of lunar volcanic action as developed in 

 their work, 'The Moon as a Planet, as a World, and a Satellite' 

 (4to, London, 1874). There is considerable ground for believing 

 that bismuth does expand in volume at or near consolidation ; but 

 with respect to all the other substances supposed to do likewise, 

 it is the object of this paper to show that the evidence is insuffi- 

 cient, and that with respect to cast iron and to the basic silicates 

 constituting iron slags, the allegation of their expansion in volume, 

 and therefore that their density when molten is greater than when 

 solid, is wholly erroneous. The determination of the specific gra- 



