264 DE. HEEMAXN KOPP OX THE EELATIOX BETWEEX BOILEN'O-POIXT 
to those hitherto noticed, the following also deserve to be mentioned, since they are like- 
wise observed in other compounds. 
The foregoing Tables afford many illustrations of the facts, that the boiling-point of an 
acid lies 63° higher than that of the methyl-ether, 44° higher than that of the ethyl-ether, 
and 13° lower than that of the amyl-ether of the same acid. These regularities appear 
to obtain in the case of acids other than those quoted. The boiling-point of monochlor- 
acetic acid (185° — 188°, R. Hoffmann) has been found about 44° higher than that of 
the monochloracetate of ethyl (143°'5, Willm). Starting ffom the boiling-point of tri- 
chloracetate of methyl (145°, Laurent), or from that of trichloracetate of ethyl (164°, 
Leblanc), the boiling-point of trichloracetic acid is found by calculation to be 208°. 
Dumas found it between 195° and 200°. From the boiling-point of monobromacetic 
acid, 208°, observed by Perkin and Duppa, that of the corresponding methyl-ether may 
be calculated at 145°, that of the ethyl-ether at 164°, and that of the amyl-ether at 221°. 
The results of observation are 144°, 159°, 207°. They are not, however, entirely to be 
relied upon, since the ethers of monobromacetic acid, and especially those possessing 
higher boiling-points, are partially decomposed by ebulhtion. 
In a few substances other than acids, the substitution of C 4 H 5 for H is occasionally 
attended by a decrease of 44° in the boiling-point ; that of Cg H 3 for H by a decrease of 
63°. Ordinary (ethyl) ether, CgHmOg, boils at 34°, i. e. 44° lower than ethyl-alcohol. 
C 4 H 0 O 2 ; methyl-amyl-ether, C 12 Hi 4 O 2 , at 72° (Williamson), i. e. 63° lower than amyl- 
alcohol, Cjo Hi 2 O 3 . If any doubt remained as to the expediency of representing ordmary 
ether by the formula Cg Hjo 02 =(C 4 H 5 )(C 4 H 5 ) 02 , instead of the formula C 4 H 5 O, this 
observation might be of some importance ; but the comparison of the boiling-pouits of 
alcohols and of so-called simple and mixed ethers, shows that the aforesaid regularity is 
not general, a circumstance arising from the fact of the elementary difference Hj, in 
the series of ethers C„H „+2 02 , involving a difference of boiling-points other than that 
corresponding to the elementary difference CgHg in the series of alcohols C^H^^oOg. 
The preceding Tables contain a great number of illustrations of the facts, that many 
compounds containing benzoyl (C 14 H 5 O 2 ) or benzyl (C, 4 H-) boil at a temperature 78° 
higher than the corresponding compounds of valeryl (Cio Hp Oo) or of amyl (Cm H,,). 
The benzoyl- and benzyl-compounds, when compared with the compounds of valeryl and 
amyl, contain 4C more and 4H less. They boil mostly, in accordance with the rules 
given (page 261), at a temperature (4xl4°'5)-l-(4x5°)=:78° higher. 
In addition to the compounds, the boiling-points of which have already been gi-v'en. 
the following exhibit the same regularity. [The mixed acetone A is the one obtained 
by the distillation of a mixture of an acetate and benzoate ; the acetone B is that 
formed by distilling an acetate and valerate. Hydride of benzyl is identical uith toluol, 
chloride of benzyl with monochlorinated toluol.] 
