especially as defined by Helinholtz. 23 



always less easily displaced by the action of alkalies than it 

 is in the parent haloid alkylic compound. 



The remarkable resemblance of the tetra-substituted am- 

 monium hydroxides to potassium hydroxide has led to their 

 being regarded as in every respect analogous to this latter, 

 and would appear to preclude the idea that they are molecular 

 compounds of an alcohol with an ammonium derivative. But 

 attentive consideration of their properties will suffice, I think, 

 to show that the apparent discrepancies are not only explic- 

 able, but that they actually support the molecular compound 

 hypothesis. Thus it might be said to be improbable that 

 tetrarnethylammonium hydroxide should behave as a 

 powerful base, and have the same heat of neutralization as 

 potassium hydroxide, if methyl-alcohol were one of its proxi- 

 mate constituents ; but it is to be remembered that the salt 

 which results from the action of an acid on methyl-alcohol is 

 liable to suffer reconversion into the alcohol by the action of 

 the water produced in the interchange ; also that in many 

 cases the methyl salt is insoluble in water, or nearly so. The 

 heat developed on neutralizing methyl-alcohol therefore falls 

 far short in amount of that which would be evolved if the 

 interchange were complete, and if the product were capable 

 of interacting with water, and perhaps also with itself in the 

 way that apparently is possible in the case of metallic salts. 

 In the case of the tetrarnethylammonium hydroxide, the 

 action of acids is total as the change is irreversible, or almost 

 so, under the conditions which obtain during the forma- 

 tion of the salt, just as in the case of the conversion of 

 potassium hydroxide into a salt ; moreover, the product is 

 easily soluble, even when acids like muriatic are used. Why 

 the methyl- alcohol, or other methyl derivative, retained in 

 the ammonium compound behaves so differently as compared 

 with the unassociated methyl derivative, is a question which, 

 for the present, we must be content to put aside unanswered. 

 I am also of opinion that in discussing their constitution, 

 no particular weight can be attached to the mode in which 

 the tetralkylic ammonium hydroxides undergo decomposition 

 when heated, as the products in some cases are an amine and 

 an alcohol, but in others an olefine and water, instead of an 

 alcohol ; in the case of the phosphonium salts the diversity is 

 still greater (Chem. Soc. Proceedings, 1886, p. 164). That 

 amines may act as " dehydrating " agents in the manner re- 

 quired, if the molecular compound hypothesis be adopted, 

 appears by no means improbable. 



What is here stated of the tetram ethyl compounds is true 

 of tetralkylic ammonium haloid compounds generally, in the 



