xi MURIATIC ACID AND CHLORINE 215 



and Bergman were unable to recognise this essential quality, 

 as in the process which they employed the water of the 

 vessels in which they received the gas " was contaminated 

 with " a portion of marine acid which always passed over in 

 the distillation." In Berthollet's apparatus this acid was 

 " retained in the first bottle," which was left empty and 

 surrounded with ice or cold water; if by chance any acid 

 passed forward it was absorbed in the first of the three bottles 

 of chlorine-water (A.C.R. XIII. 15). 



Chlorine-water purified in this way was found to have the 

 following properties : 



" It has a harsh taste which does not resemble that of the 

 acids." 



" It destroyed vegetable colours .... without any red 

 tint becoming apparent." 



" It does not cause an effervescence with solution of fixed 

 alkali, even when the latter is saturated with fixed air" 

 (A.C.R. XIII. 14). 



The fact that chlorine was not an acid was in direct 

 contradiction to Lavoisier's conception of oxygen as the 

 acid-producer. Lavoisier had concluded that muriatic acid, 

 like carbonic, nitric, sulphuric, and phosphoric acids, must 

 be a compound of oxygen ; if chlorine contained more 

 oxygen than muriatic acid it should have been a stronger 

 acid ; actually it was not an acid at all. 



This difficulty was realised by the French chemists who 

 drew up the new system of chemical nomenclature in 1787 ; 

 in proposing to describe chlorine as an " oxygenated muri- 

 atic acid " they say of muriatic acid that " it is an acid of a 

 particular nature, because it imbibes an excess of oxygen, 

 and because in this state its acidity seems rather to decrease 

 than to augment " (Chemical Nomenclature ', p. 33). 



Gay-Lussac and Thenard (1809) prove that muriatic acid 

 gas contains hydrogen. That muriatic acid gas (i) con- 



