EDITORIAL. 
377 
what  Dr.  Lowig  has  to  say  that  can  be  compressed  into  the  small  space  we 
can  devote  to  him. 
The  "  Principles  "  may  be  looked  upon  as  an  introduction  to  the  "  Che- 
mistry of  Organic  Combinations/'  (an  octavo  of  3000  pages)  which  is  now 
passing  through  its  third  edition,  and  is  intended  to  explain  more  fully  the 
author's  views  of  the  Philosophy  of  Organic  Chemistry.  The  work  is  in 
two  parts  ;  the  first  treating  of  the  constitution  and  formation  of  organic 
compounds,  and  the  Theory  of  Radicals  ;  whilst  the  second  describes  in- 
dividual substances  as  classified  by  the  author.  The  numerous  observers 
and  the  great  accumulation  of  facts  relating  to  organic  substances,  render 
more  comprehensive  and  simple  generalizations  necessary  to  classify  har- 
moniously the  phenomena  of  organic  combinations,  and  to  develope  the 
laws  which  control  their  specific  and  complex  affinities  into  a  natural  and 
truly  philosophical  system  of  arrangement.  The  work  of  Dr.  Lowig  is  an 
attempt  of  this  kind.  lie  is  a  warm  advocate  of  the  theory  of  radicals,  and 
has  endeavored  to  harmonize  the  prominent  facts  in  Dumas'  doctrine  of 
substitution  and  the  theories  of  types  and  of  nuclei  of  Laurent  and  Ger- 
hard t  therewith. 
If  the  formula  of  an  organic  compound  gives  merely  the  sums  of  its  ele- 
ments as  C8  H8  04  in  acetic  ether,  it  is  called  empirical.  If  it  groups  the 
the  atoms  as  they  are  proximatety  arrranged,  as  C4  PL,  0-f-C4  II3,  03  it  is 
then  called  rational,  because  it  explains  both  the  ultimate  and  proximate 
composition  of  the  ether  and  acetic  acid. 
An  organic  (or  compound)  radical  is  a  group  of  atoms  combined,  so  as  to 
act  as  a  simple  element  in  a  series  of  compounds,  of  which  it  forms  the 
characteristic  ingredient.  Thus,  nitrogen  in  the  five  oxides  of  nitrogen,  is 
a  simple  (^organic)  radical;  whilst  ethyl,  C4  II5,  is  an  organic  radical,  be- 
cause the  oxygen  of  its  oxide,  ether,  may  be  replaced  by  chlorine,  bromine, 
iodine  etc.,  just  as  though  it  was  a  simple  body,  and  belongs  to  the  primary 
class.  A  second  series  results  when  the  hydrogen  of  the  radical  is  partially 
or  wholly  replaced  by  other  elements  ;  as  when  acetyl  C4  H3  becomes  chlor- 
acetyl  C4  Cl3  by  the  substitution  of  chlorine;  or  when  valeryl  C10  H9  becomes 
C10  H7  Cl2.  Such  are  called  derived  radicals.  Owing  to  this  law  of  substi- 
tution the  derivative  compounds  are  extremely  numerous,  yet,  as  a  certain 
mutual  relation  exists  among  substances  traceable  to  a  common  primary 
radical,  they  constitute  a  natural  group  or  family.  It  frequently  happens 
that  two  radicals  unite  to  form  a  more  complex  one ;  in  such  cases  the  com- 
bining capacity  is  generally  determined  by  but  one  of  them,  in  which  case 
the  indifferent  body  is  called  the  pairling,  the  other  the  active  molecule,'  thus 
(C4  H2)^~"C2  H,  in  which  C4  H2  is  the  pairling.  The  following  extract  will 
exhibit  the  author's  view  of  the  constitution  of  the  most  extensive  or  hydro- 
carbon class  of  radicals. 
"By  far  the  greater  number  of  organic  compounds  are  to  be  traced  back 
to  radicals  which  consist  of  carbon  and  hydrogen,  and  were  called  above 
Hydro  carbyls.  By  an  accurate  observation  and  comparison  of  these  in  every 
aspect  which  they  present,  it  is  found  that  they  belong  to  different  groups, 
