PLEASE SCROLL DOWN FOR ARTICLE This article was downloaded by: [University of Oxford]On: 13 May 2010Access details: Access Details: [subscription number 909667651]Publisher Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37- 41 Mortimer Street, London W1T 3JH, UK Philosophical Magazine Series 3 Publication details, including instructions for authors and subscription information: http://www. informaworld.co m/smpp/title~con tent=t910848352 XLV. Theory of ætherification Alexander Williamson a a London University, To cite this Article Williamson, Alexander(1850) 'XLV. Theory of ætherification', Philosophical Magazine Series 3, 37: 251, 350 — 356 To link to this Article: DOI: 10.1080/14786445008646627 URL: http://dx.doi.org/10.1080/14786445008646627 Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
This article was downloaded by: [University of Oxford]
On: 13 May 2010
Access details: Access Details: [subscription number 909667651]
Publisher Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-
41 Mortimer Street, London W1T 3JH, UK
Philosophical Magazine Series 3Publication details, including instructions for authors and subscription information:http://www.informaworld.com/smpp/title~content=t910848352
XLV. Theory of ætherificationAlexander Williamson a
a London University,
To cite this Article Williamson, Alexander(1850) 'XLV. Theory of ætherification', Philosophical Magazine Series 3, 37: 251,350 — 356
To link to this Article: DOI: 10.1080/14786445008646627
URL: http://dx.doi.org/10.1080/14786445008646627
Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf
This article may be used for research, teaching and private study purposes. Any substantial orsystematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply ordistribution in any form to anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representation that the contentswill be complete or accurate or up to date. The accuracy of any instructions, formulae and drug dosesshould be independently verified with primary sources. The publisher shall not be liable for any loss,actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directlyor indirectly in connection with or arising out of the use of this material.
X L V . Theo~:yo f _~therioEcation. B y A L ~ X A ~ D r m W 1 L L I A I ~-
SON, Professor o f Practical Chemist~F] in the Lon don U ni-versitg*.
WH E N s u l p h u r lc a ci d is b r o u g h t in c o n t a c t w i th a l co h o l
u n d e r c e r ta i n c i r c u m s t an c e s , a n e w a r r a n g e m e n t ise f fe c te d i n t h e e l e m e n t s o f t h e a l c o h o l , w h i c h d i v i d e i n t o t w o
t ~o u p s~ f o r m i n g ~ t h e r a n d w a t er . N o w i t is w e ll k n o w n t h a te p r o c e s s b y w h i c h t h is c h a n g e is e f fe c te d m a y b e r e p r e -
s e n t e d in t w o w a y s , t h e d i f fe r e n c e o f w h i c h c o n s i st s i n t h e i rr e s p e c t i v e l y se l e c t i n g f o r s t a r t i n g - p o i n t a d i f I h r e n t v i e w o f t h e
c o n s t i tu t i o n o f a l c o h o l . A c c o r d i n g t o t h e o n e v i ew , a n a t o mo f a l c o h o l w e i g h s 2S~ a n d is m a d e u p o f C 2 H 6 O ; s o t h a t t of o r m ~ e th er, t w o a t o m s o f i t a r e n e e d e d , o n e o f w h i c h t a k e sC a H 4 f r o m t h e o t h e r , s e t ti n g f r ee t h e w a t e r w i t h w h i c h t h e s ee l em e n t s w e re c o m b i n e d ; w h e r ea s, a c c o r d i n g to t h e o t h e rv i e w , a l c o h o l w e i g h s 4 6 , a n d contains r a th e r a n d w a t e r . T h e s ea r e n o t t h e o n l y p o i n t s o f d i f fe r e n c e w h i c h a r e u r g e d ; b u t
t h e y a r e t h e m o s t r e a l a n d t a n g i b le , a n d t h e i r c o n s i d e r a t i o n iss u ff ic ie n t f o r o u r p r e s e n t p u r p o s e . I f b y a n y d i r e c t f a ct w ec o u l d d e c i d e w h i c h o f t h e s e tw o e x p r e s s i o n s is t h e c o r r e c to n e , t h e g r o u n d w o u l d b e c l e a r f o r a n e x a m i n a t io n o f t h ep r o c e s s o f ~ e t h e ri fi c at io n it se lf . I n o r d e r t o s h o w m o r e c l e a r l yt h e t r u e m e a n i n g o f t h e f a ct s I h a v e t o a d d u c e o n t h i s p o i n b1 w ill b r i n g t h e m b e f o r e y o u in t h e o r d e r in w h i c h t h e y a r o s e,
M y o b j e c t in c o m m e n c i n g t h e e x p e r i m e n t s w a s t o o b t a i nn e w a lc o h o ls b y su b s t it u ti n g c a r b u r e t t e d h y d r o g e n f o r h y -
d r o g e n in a k n o w n a l c o h o l . W i t h t h is v ie w I h a d r e c o u r s et o a n e x p e d i e n t , w h i c h m a y r e n d e r v a l u a b l e s e rv i c e s o n s i m i l a r
o c c a s io n s . I t c o n s i s t e d i n r e p l a c i n g t h e h y d r o g e n f ir st b y
p o t as si u m , a n d a c ti n g u p o n t h e c o m p o u n d t h u s f o r m e d b y t h ec h l o r i d e o r i o d id e o f t h e c a r b u r e t t e d h y d r o g e n w h i c h w as t ob e i n t r o d u c e d in t h e p l a ce o f t h a t h y d r o g e n . I c o m m e n c e dw i t h c o m m o n a l c o h o l , w h i c h , a f t e r c a re f u l p u r i f i c at i o n , w a ss a t u r a t e d w i t h p o ta ss iu m ~ a n d a s s o o n a s t h e a c t i o n b a d c e a s e d ,
m i x e d w i th a p o r t i o n o f io d i d e o f e e th y l e e q u i v a l e n t t o t h e p o -t a ss i u m u s e d . I o d i d e o f p o t a s s i u m w a s r e a d i l y f o r m e d o n t h ea p p l i c a t io n o f a g e n t l e h e a t , a n d t h e d e s i r e d s u b s t i t u t i o n w a se ff ec te d ; b u t , to m y a s to n i s h m e n t , t h e c o m p o u n d t h u s f o r m e d
h a d n o n e o f t h e p r o p e r t i e s o f a n a l c o h o l - - i t; w a s n o t h i n g e l set h a n c o m m o n r a t h e r , C a H 10 O .N o w t h i s r e s u l t a t o n c e s t r u c k m e a s b e i n g i n c o n s i s t e n t
w i th t h e h i g h e r f o r m u l a o f a l co h o l ; f o r i f t h a t b o d y c o n t a i n e dt w i c e a s m a n y a t o m s o f o x y g e n a s a r e in , e th e r , I o u g h t c l e a r l y
* Com mu nicated by the Au thor ; having been read before the B ritishAssociation at Edinburgh, August 3, 1850.
Mr. A. Williamson's Th eory o f -/~,the~/~cation. aS1
to have obtained a product containing twice as much oxygenas tether does. The alternative was evident; for having ob-
tained tether by substituting C u H 5 for H in alcohol, the rela-tive composition of the two bodies is represented by expressing
C a H 5t ha t f a c t i n our f o rmu l a . Thus alcohol is H O, and the
C a H 5potassium compound is K O; and by acting upon this by
iodide of tethyle, we haveC ~H 5
K O+C~HSI=IK+ C~HS-Ca H50.
Of course the proportion between the two bodies is the onlypoint upon which I here enter, and the same reasoning wouldbe applicable to any multiple of the formulae assumed. Somechemists may perhaps prefer doubling them in order to avoidthe use of atoms of hydrogen, potassium, &c. ; but I have notfelt myself justified in doing so, because that would involvedoubling the usual formula fbr water ; tbr, as I will presentlyshow, water is formed in tetherification by replacing the car-buretted hydrogen of alcohol by hydrogen, which, of course,
obliges us to assume the same unity of oxygen in both. Alcoho|is therefore water in which halt" the hydrogen is replaced bycarburetted hydrogen, and tether is water in which both atomsof hydrogen are replaced by carburetted hydrogen : thus,
H C ~ H 5 C 2 H ~H 0, H O, C ~ H 50.
This formation of tether might however be explained aftera fashion by the other theory--by supposing the potassium
compound to contain tether and potash, which separate duringthe action of the iodide of tethyle ; so that half the tether ob-tained would have been contained in that compound, and theother half formed by double decomposition between potashand iodide of tethyle : th us --
C 4H,0K~ O+C4 H'°I~=2IK+2(C4 H '° 0).
But Mthough the insufficiencyof this explanation becomesevident on a little reflection, I devised a furtherand more tan-
gible method of arriving at a conclusion. It consisted in act-ing upon the potassium compound by iodide of methyle, nwhich case I should, if that compound were nether and potash,obtain a mixture of tether and oxide of methvle; whereas inthe contrary case I should obtain a body of the compositionCz H80. Now this substance I obtained, and neither tethernor oxide of methyle.
8 5~ M r . A . W i l l ia m s o n ' s Theory o f~theri j fcat ion.
I n t h i s e x p e r i m e n t t h e t w o t h e o r i e s c r o s s o n e a n o t h e r , a n dm u s t l e a d t o d i f f e r e n t r e s u l t s ; f o r i t i s e v i d e n t t h a t , i n t h e
f i r s t - m e n t i o n e d d e c o m p o s i t i o n b y w h i c h n e t h e r w a s f o r m e d ,t h e o n l y d i f fi c u l ty i n e x p l a i n i n g t h e p r o c e s s d e c i s iv e l y c o n s i s te di n o u r i n a b i l i t y t o p r o v e t h a t t h e c a r b u r e t t e d h y d r o g e n i n t r o -d u c e d i n s te a d o f t h e h y d r o g e n d i d n o t h a v e i n t h e p r o d u c t a na t o m o f o x y g e n t o i t se lf , b u t t h a t , o n t i le c o n t r a r y , i t w a sc o u p l e d w i th t h e c a r b u r e t t e d h y d r o g e n a l r e a d y c o n t a i n e d i nt h e a l c o h o l - - t h e t w o i n c o m b i n a t io n w i t h o n e a t o m o f o x y g e n .I t i s c l e a r t h a t i f a l c o h o l contain n e t h e r a n d w a t e r , a n d t h ee a r b u r e t t e d h y d r o g e n i n m y f i rs t e x p e r i m e n t f o r m e d a s e c o n d
a t o m o f n e th e r b y t a k i n g t il e p l a c e o f t h e h y d r o g e n o f t h i sw a t e r , t h a t t h e p r o c e s s b e i n g t h e s a m e i n t h e s e c o n d e x p e r i -m e n t , w e sh o u l d t h e n h a v e o b t a i n e d t w o n eth er s. W h e r e a s i ft h e f o r m a t i o n o f n e th e r f i'o m a l c o h o l b e e f f e c te d b y s y n t h e s i s ,a n e w e a r b u r e t t e d h y d r o g e n b e i n g a d d e d t o t h e o n e a l r e a d yc o n t a i n e d i n t h e a l c o h o l , w e o u g h t t o o b t a i n t il e n e w i n t e r m e -d ia te ve.ther w hich I o b ta ine d .
T h e c o m p l e te d e s c r ip t i o n o f t h i s r e m a r k a b l e b o d y , a n d o fi t s d e c o m p o s i t i o n s , w i l l f o r m t h e s u b j e c t o f a f u t u r e p a p e r . Iw i l l n o w m e r e l y s t a te t h a t i ts b o i l i n g - p o i n t i s a l i tt l e a b o v e10 ° Cen t . ; i t i s pos se s sed o f a v e ry pecu l ia r sme l l , d i s t inc t lyd i f fe r e n t f r om t h a t o f c o m m o n n e th e r ; a n d , l ik e t h a t b o d y , i ti s o n l y s l i g h t l y s o l u b l e i n w a t e r . I t i s n o t a c t e d u p o n b y t h ea l k a l i - m e t a l s a t t h e c o m m o n a t m o s p h e r i c t e m p e r a t u r e .
B y a c t i n g u p o n t h e p o t a s s i u m - a l c o h o l in l i k e n m n n e r b yi o d i d e o f a m y l e , I e f f ee t ed a s i m i l a r s u b s t i t u t i o n o f t il e e l e -m e n t s o f t h a t e a r b u r e t t e d h y d r o g e n it] th e p l a c e o f t h e h y -d r o g e n o f a l c o h o l , a n d o b t a i n e d a n n e th e r b o i l i n g a t 1 11 ° C . ,h a v i n a t h e c o m p o s i t i o n C 7 H 16 O . T h e r e i s s o m e r e a s o n t o
b e li ev e t h a t th i s b o d y is t h e s a m e w h i c h B a l a r d o b t a i n e d b yd e c o m p o s i ti o n o f c h l o r i d e o f a m y l e b y a n a l c o h o li c s o l u t i o no f h y d r a t e d p o t a s h, a n d w h i c h t h a t d i s t in g u i s h e d c h e m i s t t o o kf o r o x i d e o f a m y l e .
F r o m t h e p e r f e ct a n a l o g y o f p r o p e rt ie s b e tw e e n t h e k n o w nt e r m s o f t h e a l c o h o l i c s e ri es , i t w a s t o b e e x p e c t e d t h a t s i m i l a rs u b s t i t u t io n s m i g h t b e e f f e ct e d i n t h e o t h e r s ; a n d I h a v e v e-r if ie d t h is b y e x p e r i m e n t . O f c o u r s e t h e f or m u ln e o f t h e o t h e ra l c o h o l s m u s t b e r e d u c e d t o h a l f , f o r t h e s a m e r e a s o n s a s t h a t
o f c o m m o n a l co h o l . M e t h y l i e a l c o h o l is t h e r e f o r e e x p r e s s e dHHs C~2 H 5b y t h e f o r m u l a C 0 , a s c o m m o n a l co h o l is H 0 ; a n d
C ~ H ni n t h e s a m e m a n n e r a m y l i c a l c o h o l is H O , a n d t h e s a m e
o f t h e h i g h e r o n e s . I n c o n f o r m i t y t o t h i s f a c t, w e m u s t b ea b l e t o o b t a i n t h e s a m e i n t e r m e d i a t e n et he rs b y r e p l a c i n g h y -d r o g e n i n t h e s e a l c o h o l s ( m e t h y l i e a n d a m y l i c ) b y t h e c a r b u -
M r . A . W i l l ia m s o n ' s 7-heor# ~'ZE theri/ication. 353
r e t t e d h y d r o g e n o f i o d i d e o f ~ e th y le , a s b y t h e i n v e r s e p r o c e s sdesc r ibed above . T h i s I have ve ri f ied ill the ea se o f ti l e th re e -c a r b o n ~ e th e r, w h i c h m a y b e o b t a i n e d i n d i f f e r e n t l y b y r e p l a -c i n g o n e - f o u r t h o f t h e h y d r o g e n o f m e t h y l i e a l co h o l b y C ~ [ t 5,o r b y r e p l a c i n g o n e - s i x th o f t il e h y d r o g e n o f c o m m o n a l c o h o l
b y C H 8. I t s r a t io n a l f o r m u l a i s t h e r e f o r e C ~ H 5
B y a c t i n g u p o n t h e c o m p o u n d C H 3 C H a O .K O b y i o d i d e o f a m y l e ,
I o b t a i n e d a t h i r d ~ e th e re a l e o m p o u n d , o f w h i c h t h e f o r m u l a
is CCs H aU O . T h i s i s e v i d e n t ly t h e o n l y o n e o f t h e t h r e e n e w
~ e th e rs , w h i c h , c o n t a i n i n g a n e v e n n u m b e r o f" c a r b o n a t o m s ,m i g h t h e c o n c e iv e d t o h a v e b e e n f o r m e d t i'o m o n e a l c o h o l ;b u t w h e n t r e a t e d w i th m o n o b a s i c a c i ds , a s h y d r o c h l o r i c , i tc a n n o t b e e x p e c te d t o a c t in t h e s a m e m a n n e r a s i t s h o m o g e °
C ~ t Vn e o u s i s o m e r i c , the ~ e th e r C a H 7 0 o f t h e t h r e e - c a r b o n a l c o h o lC 3 H 7
H O ; bu t o f th i s ! w i ll g ive an exac t acc ou n t in the pa pe r
a b o v e a l l u d e d t o .
M y t a s k i s n o w t o e x p l a i n t h e p r o c e s s o f e e t h e r i f i c a ti o n b y t h ea c t i o n o f s u l p h u r i c a c i d ( S O 4 H 2) u p o n a l c o h o l ; a n d i n o r d e r t oa c c o m p l i s h t h a t , I m u s t s ho w t h e c o n n e x i o n b e tw e e n t h o s e s u b -s t a n c e s a n d t h e r e a g e n t s u s e d i n t h e a b o v e - d e s c r i b e d e x p e r i -m e n t s . W i t h t h is v ie w , I h a v e m e r e l y t o a d d t o t h e ah o v et he ts th e a c k n o w l e d g e d a n a l o g y o f th e s i m p l e a n d c o m p o u n dr a d i c a l s i n t h e i r c o m p o u n d s . I m u s t f i rs t s h o w h o w a s u b -s t a n c e a n a l o g o u s t o m y i o d i d e o f e e th y l e i s f o r m e d , a n d t h e nh o w b y d o u b l e d e c o m p o s i ti o n w it h a l c o h o l it p r o d u c e s t e th e r .T h i s is v e r y e a s y ; f o r s u l p h o v i n i e a c i d i s s t r i c t ly a n a l o g o u st o i o d i d e o f ~ e th y le p l u s i o d i d e o f h y d r o g e n , w h i c h w e s h o u l do b t a i n b y r e p l a c i n g S O 4 i n i t s f o r m u l a b y a n e q u i v a l e n t o fi o d i n e ; a n d i n o r d e r t o r e p r e se n t t h e f o r m a t i o n o f t h is s u l-p h o v i n i c a c i d , w h i c h i s w e l l k n o w n t o p r e c e d e t h a t o f ~ e t h e r ,t h e s i m p l e s t m o d e is a t t h e s a m e t i m e t h e o n e m o s t fi'e e f r o mh y p o t h e s i s ; i t c o n s is t s i n s t a t i n g t h e f a ct , t h a t s u l p h u r i c a c i da n d a l co h o l a re t r a n s t b r m e d i n t o su l p h o v i n ic a c i d a n d w a t e r ,b y h a l f t h e h y d r o g e n o f t h e f o r m e r c h a n g i n g p la ce s w it h t h ec a r b u r e t te d h y d r o g e n o f t h e l a t t e r : t h u s - -
H HH 8 0 4 C ~ H 5 S 0 4
C ~ H 5H O H O
N o w f r o m t h i s p o i n t i t i s c l e a r t h a t t h e p r o c e s s i s t h e s a m e a sin the de com pos i t io ns above , de sc r ib ed ; tb r by th i s su lph ov in ie
P hi l . Mag . S. 3 .V ol . 37 . N o. ~251. ~Tov. 1850. o A
3 54 M r . A . W i l l ia m s o n ' s Theo t9 o f ~ t h e r i f t c a t i o n .
a c id c o m i n g i n co n t a c t w i t h a n a t o m o f a l c o h o l , i t r e a ct s e x -a c t ly i n t h e s a m e m a n n e r a s t h e i o d i d e d i d , f o r m i n g o f c o u r ses u l p h u r i c a c i d a n d o e t h er :
H HC ~ H 5 SO 4 H SO 4
H C ~ H 5C~ H ~ O C ~ H 5 0
T h e s u l p h u r i c a ci d t h u s r e p r o d u c e d c o m e s a g a i n i n c o n t a c tw i t h a l c o h o l , f o r m i n g s u ] p h o v i n i c a c i d , w h i c h r e a c t s a s b e f o r e ;a n d s o t h e p r o c e s s g o e s o n c o n t i n u o u s l y , a s f o u n d i n p r a c t i c e .
W e t h u s s e e t h a t t h e f o r m a t i o n o f r a th e r f r o m a l c o h o l i sn e i t h e r a p ro c e s s o f s i m p l e s e p a r a ti o n , n o r o n e o f m e r e s y n -t h e s i s ; b u t t h a t i t c o n si s ts i n t h e s u b s t i t u t i o n o f o n e m o l e c u l ef o r a n o t h e r , a n d i s e f f e c t e d b y d o u b l e d e c o m p o s i t i o n b e t w e e nt w o c o m p o u n d s . I t h e r e f o r e a d m i t t h e c o n t a c t t h e or y ~ i n a s -m u c h a s I a c k n o w l e d g e t h e c i r c u m s t a n c e o f c o n t a c t a s a n e -c e s s a r y condit ion o f t h e r e a c t i o n o f t h e m o l e c u le s u p o n o n ea n o t h e r . B y r e d u c i n g t h e f orm u la ~ o f t h e a l c o h o l s t o o n e a t o mo f o x y g e n , I a ls o r e ta i n t h e e q u a l i t y o f v o l u m e s w h i c h t h e c o n -
t a c t t h e o r y i n s is t s u p o n b e t w e e n t h e v a p o u r s o f t h e s e b o d i e sa n d t h e i r m t h e r s , s o t h a t ~ e t h e r t r u l y c o n t a i n s t h e e l e m e n t s o fo l e f ia n t g a s i n a d d i t io n t o t h o s e o f a l c o h o l in o n e a t o m . B u t ,o n t h e o t h e r h a n d , I a t t a c h e q u a l i m p o r t a n c e t o a ll t h e e s s e n -t ia l f a c ts o f t h e c h e m i c a l th e o ry ~ a n d r e s t m y e x p l a n a t i o n o ft h e p r o c e s s a s m u c h u p o n t h e m a s u p o n t h o s e o f t h e c o n t a c tt h e o r y ; f o r, o n e - s i x th o f th e h y d r o g e n i n a l c o h o l t r u l y e x -h i b i t s d i f f e r e n t r e a c t i o n s f r o m t h e r e m a i n i n g f i v e , a n d m u s tt h e r e f o r e b e c o n t a i n e d i n t h a t c o m p o u n d i n a d i f f e re n t m a n n e rf r om t h e m ; a n d t h e a l te r n a te f o rm a t i o n a n d d e c o m p o s i ti o no f s u l p h o v i n i c a c i d i s t o m e , a s t o t h e p a r t is a n s o f t h e c h e m i c a lt h eo r y ~ t h e k e y t o e x p l a i n i n g t h e p r o c e s s o f r e t h e ri f ic a t i o n .
I n n o v a t i o n s i n s c ie n c e f r e q u e n t l y g a i n g r o u n d on l b y d i s -p l a c i n g t h e c o n c e p t io n s w h i c h p r e c e d e d t h e m , a n d w h i c h s e r v e dm o r e o r l es s d i r e c t l y a s t h e i r f o u n d a t i o n ; b u t , i f t h e v ie w w h i c hI h a v e h e r e p r e s e n t e d b e c o n s i d e r e d a s te p i n o u r u n d e r s t a n d -i n g o f t h e s u b j e c t, I m u s t b e g l e a v e t o d i s c l a im f o r i t th e t i tl eo f i n n o v a t i o n ; f o r m y c o n c l u s i o n c o n s is t s i n e s t a b l i s h i n g t h ec o n n e x i o n a n d s h o w i n g t h e c o m p a t i b i li t y o f v ie w s w h i c h h a v e
h i t h e r t o b e e n c o n s i d er e d c o n t r a r y ; a n d t h e b e s t p o s s ib l e j u s -t i f ic a t i o n o f th e e m i n e n t p h i l o s o p h e r s w h o a d v .o c a te d e i t h e ro n e o f t h e t w o c o n t e n d i n g th eo ries~ i s t h u s a f f o r d e d b y m yr e c o n c i l i n g t h e i r a r g u m e n t s w i th t h o s e o f t h e i r e q u a l l y i l lu s -t r i o u s o p p o n e n t s .
B e f o r e q u i t t i n g t h e s u b j e c t o f ~ e t h e ri f ic a ti o n , I w o u l d w i s ht o a d d a f e w w o r d s o n a n a p p l i c a t i o n w h i c h n a t u r a l l y e n o u g h
M r . A . W i l li a m s o n ' s Theory of . /J~therifcation. 355
s u g g e s t s i t s e l f o f t h e f a c t t o w h i c h t h e p r o c e s s i s h e r ea s c ri b e d . I r e f e r t o t h e tr a n s f e r o f h o m o l o g o u s m o l e c u l e s i na l t e r n a t e l y o p p o s i t e d i r e c t i o n s , w h i c h , a s I h a v e e n d e a v o u r e dt o s h o w , i s t h e c a u s e o f th e c o n t i n u o u s a c ti o n o f s u l p h u r i e a c i di n t h is r e m a r k a b l e p ro c e ss . I t m a y n a t u r a l l y b e a s k e d , w h yd o h y d r o g e n a n d c a r b u r e t t e d h y d r o g e n t h u s c o n t i n u o u s l yc h a n g e p l a c e s ? I t c a n n o t b e f r o m a n y su c h c i r c u m s t a n c e a ss u p e r i o r a f fi n it y o f o n e m o l e c u le o v e r a n o t h e r , f o r o n e m o m e n ts e e s r e v e r s e d w i t h a n e w m o l e c u l e t h e t r a n s f e r e f f ec t e d d u r i n gt h e p r e c e d i n g o n e . N o w i n r e f le c ti n g u p o n t h is r e m a r k a b l ef a c t , i t s t r i k e s t h e m i n d a t o n c e t h a t t i l e fa c i li t y o f i n t e r c h a n g e
m u s t b e g r e a t e r t h e m o r e c l o s e t h e a n a l o g y b e t w e e n t h e m o -l e cu l es e x c h a n g e d ; t h a t i f h y d r o g e n a n d a m y l e c a n r e p l a c eo n e a n o t h e r i n a c o m p o u n d , h y d r o g e n a n d o e th y le , w h i c h a r em o r e n e a r l y a ll ie d i n c o m p o s i t io n a n d p r o p e r t i e s , m u s t b e a b l et o re p l a c e o n e a n o t h e r m o r e e a si ly i n t h e s a m e c o m p o u n d ;a n d t h a t t h e f a ci li ty o f i n t e r c h a n g e o f h y d r o g e n a n d m e t h y l e ,w h i c h a r e st il l m o r e s i m i l a r , w i ll b e s ti ll g r e a t e r . B u t i f t h i sb e t r u e , m u s t n o t t h e e x c h a n g e o f o n e m o l e c u le f o r a n o t h e r o fidentical p r o p e r t i e s b e t h e m o s t e a s il y e f fe c te d o f a l l ? S u r e l y
i t m u s t , i f t h e r e b e a n y d i f fe r e n c e a t ' a l l ; a n d i f s o, t h e l a w o fa n a l o g y f o rb i d s o u r i m a g i n i n g t h e f a c t t o b e p e c u l i a r t o h y -d r o g e n a m o n g s u b s ta n c e s r e s e m b l i n g i t i n o t h e r r e sp e c ts .W e a r e th u s t b rc e d t o a d m i t , t h a t , i n a ll a g g r e g a t e o f m o l e -c u le s o f a n y c o m p o u n d , t h e r e is a n e x c h a n g e c o n s t a n t l y g o i n go n b e t w e e n t h e e l e m e n t s w h i c h a r e c o n t a i n e d i n i t. F o r i n -s ta n c e , a d r o p o f h y d r o c h l o r i c a c i d b e i n g s u p p o s e d t o b e m a d eu p o f a g r e a t n u m b e r o f m o l e c u l es o f t h e c o m p o s i t io n C I H ,t h e p r o p o s i t i o n a t w h i c h w e h a v e j u s t a r r i v e d w o u k t l e a d u st o b e li ev e t h a t e a c h a t o m o f h y d r o g e n d o e s n o t re m a i n q u i e t l yin j u x t a p o s i t i o n w i th t h e a t o m o f c h l o r i n e w i t h w h i c h i t f i rs tu n i t e d , b u b o n t h e c o n t r a r y , i s c o n s t a n t l y c h a n g i n g p l a c e sw i t h o t h e r a t o m s o f h y d r o g e n , o r , w h a t i s t h e s a m e t h i n g ,c h a n g i n g c h l o r in e . O f c o u r s e t h is c h a n g e i s n o t d i r e c t l y s e n -s ib l e t o u s, b e c a u s e o n e a t o m o f h y d r o c h l o r i c a c i d is l i k ea n o t h e r ; b u t s u p p o se w e m i x w i th t h e h y d r o c h l o r i c a c id s o m es t d p h a t e o f c o p p e r ( o f w h i c h t h e c o m p o n e n t at o m s a r e u n d e r -g o i n g a s i m i l a r c h a n g e o f p l a c e ) , t h e b a s i l o u s e l e m e n t s h y -d r o g e n a n d c o p p e r d o n o t l im i t t h e i r c h a n g e o f p l a ce t o t h e
c i r c le o f t h e a t o m s w i t h w h i c h t h e y w e r e a t f i r s t c o m b i n e d , t h eh y d r o g e n d o e s n o t m e r e l y m o v e f k om o n e a to m o f c h l o r i n e t oa n o t h e r , b u t in i ts t u r n a ls o r e p la c e s a n a t o m o f c o p p e r , f o r m -i n g c h l o r i d e o f c o p p e r a n d s u l p h u r i c a ci d . T h u s i t is , t h a t a ta n y m o m e n t o f t im e i n w h i ch w e e x a m i n e th e m i x t u r e , t h eb a s es a r e d i v i d e d b e t w e e n t h e a c i d s ; a n d i n c e r t a i n c ases~w h e r e t h e d i f f e r en c e o f p r o p e rt i es o f t h e a n a l o g o u s m o l e c u l e s
$56 Mr. A. Williamson's Theo ry of~the riflcation.
is very great, it is found that the stronger acid and strongerbase remain almost entirely together, leaving the weaker onescombined. Tills is well known in the case of a mixture ofsulphm'ic acid and borax, and is a confirmation of our funda-mental assumption, that the greater the difference of proper-ties, the more difficult is the alternate interchange of one mole-cule for another.
But suppose now that instead of sulphate of copper, wemixed sulphate of silver with our hydrochloric acid in aqueoussolution, and that a similar division of the bases between theacids established itself in the first moment, fbrming four com-
poumls, SO4H ~, SO4Ag~, CIH, CIAg; it is clear that thislast-mentioned compound, being insoluble in water, must, onits fbrmation, separate out and remove fiom the circle of de-compositions which solubility established. But ofcou rs~ thethree compounds remaining in solution continue the exchangeof their component parts, and give rise successively to newportions of chloride of silver, until as much of that compoundis precipitated as the liquid contained equivalents of its com-ponent parts, a very small quantity remaining in solution and
in the circle of decompositions.Such is the general process of chemical decomposition.Of course a compound is removed as effectually fi'om the circleof decompositions by possessing the gaseous form under thecircumstances of the experiment, or even by being a liquidinsoluble in the menstruum. I believe this explanation coin-cides in its second part with the one proposed manyyears agoby Berthollet; but not making use of the atomic hypothesis,upon which nay explanation is based, that eminent philosopher
went no farther back than the division of the acids betweenthe bases on the mixture of salts, a thct which I have herededuced fi'om the motion of atoms. It is well known that thegeneral thct upon which Berthollet founded his view is deniedby some eminent chemists of the present day; but I believethe instances which they adduce are only apparent exceptionsto the law, and will on further examination be found to affordadditional confirmation of the truth of the great Savoysien'sconception, as l have shown in the case of boracic and sul-phuric acids.
In using the atomic theory, chemists have added to it oflate years an unsafe, and, as I think, an unwarrantable hy-pothesis, namely that the atoms are in a state of rest. Nowthis hypothesis I discard, and reason upon the broader basisof atomic motion.
