1908-9.] Life and Chemical Work of Archibald S. Couper. 209 
plained, I completely agree with Butlerow in this interpretation of ?iM 4 . 
But if we make this assumption for the type ^C 2 M 4 ( = wCM 4 ), we must 
do the same for the second type wC 2 M 4 — mM 2 , and that is what Butlerow 
does not do, for he says of this type : — “ Die zweite typische Formel ')iC 2 M 4 — 
mM 2 ” (%CM 4 -mM 2 ) “ wenn der Strich ( — ) das Zeichen der Verbindung 
vorstellen soli, wie in anderen Formeln von Couper, stimmt mit den That- 
sachen auch nicht iiberein ; soil sie aber als tiC 2 M 4 minus mM 2 verstanden 
werden, so bekonunt man ftir n— 7, m = 6 z.B. C 14 H 28 — 12H = C 14 H 16 , das 
heisst eine Verbindung mit der moglichst grossen Menge von Wasserstoff. 
— Die Verbindung C 12 H 6 aber, ihre Homologen, Naphtalin, u.s.w. wo der 
Verbindungsgrad nicht der Formel C 2w H 2w+2 und sogar nicht der Proportion 
C 2n H 2n entspricht, durcli welche allgemeine Formeln sollen sie vorgestellt 
werden ? ” 
Kekule also, as I have shown above, misunderstood the expression. 
I note first that in the formula the stroke ( — ) is clearly a minus sign 
and not a mark of combination. If we keep in view that the first term 
of the second type is identical with the first type, and must have the same 
meaning, so that M stands for a unit of affinity, then we see that nC M 4 is 
the type for all saturated carbon compounds in the second type also. If 
then ^M 2 units of affinity are to be subtracted from ?iCM 4 (because they 
are not saturated), the expression ^CM 4 — mM 2 is the type of those carbon 
compounds which we call unsaturated. Benzene and naphthalin, the 
examples chosen by Butlerow, can be referred without any difficulty to 
this type. Let n = 6 and m = 4, then, if no element but hydrogen is 
present with the carbon, we have : 
?zCM 4 — ??iM 2 
C 6 H 14 - 814 = C 6 H 6 = Benzene. 
Let n = 10 and m = 7, then we have 
%CM 4 - mM 2 
Ci 0 H 22 - 14H = C 10 H 8 = Naphthalin. 
In the first case supposed by Butlerow, on the assumption of n = 7 and 
m = 6, we should have for 
?iCM 4 - mM 2 
(or ?iC 2 M 4 - mM 2 ) 
not C 7 H 2S - 12H = C 7 H 16 (or C 14 H 2S - 12H = C 14 H 16 ) 
but C 7 H 16 - 1 2H = C 7 H 4 (or C 14 H 16 - 1 2H = C 14 H 4 ). 
That would be a formula in which 7C (or 7C 2 ) are united by 12 carbon 
affinities, leaving 4 affinities over for union with hydrogen. 
The most difficult thing to understand in Couper’s view is how he 
VOL. xxix. 14 
