Am.  Jour.  Pharm, ") 
;.Oct.,  1883.  J 
Basis  of  Thermo- Chemistry. 
527 
tissue  is  immediately  disintegrated  into  its  constituent  cells.  Its  deter- 
mination is  effected  by  heating  the  tissue  in  the  cold  with  dilute  hydro- 
chloric acid,  which  decomposes  the  calcium  pectate,  leaving  the  pectic  acid 
in  an  insoluble  state ;  this  is  then  heated  with  a  dilute  solution  of  potassa, 
producing  a  soluble  pectate  which  can  be  again  decomposed  by  acids. 
6.  The  Nitrogenous  substances  contained  in  vegetable  tissues  are  dissolved 
by  alkalies. 
7.  The  Inorganic  substances  constitute  the  ash  after  calcination. 
In  woods  the  proportion  of  vasculose  increases  with  their  hardness  and 
density.  The  proportions  of  cellulose  and  paracellulose  vary  in  stems  ;  pine 
wood  appears  to  be  composed  exclusively  of  paracellulose  and  vasculose. 
The  parenchyma  of  the  pith  often  contains  considerable  quantities  of  pectose 
and  calcium  pectate.  Cork  consists  partly  of"  suberin,"  and  is  composed 
of  cutose  and  vasculose.  In  leaves  and  petals  the  parenchyma  consists  of 
cellulose  and  pectose,  and  the  vascular  bundles  and  vessels  of  vasculose  and 
paracellulose.  The  utricular  tissue  of  petals  is  composed  almost  entirely  of 
cellulose,  thin  spiral  vessels  almost  entirely  of  vasculose. 
Vasculose  can  be  obtained  in  special  purity  from  the  pith  of  the  elder. 
After  treating  with  dilute  alkali  it  is  boiled  with  dilute  hydrochloric  acid 
in  order  to  transform  the  paracellulose  into  cellulose ;  the  ammoniacal 
copper  reagent  is  then  used,  and  the  treatment  repeated  eight  or  ten  times 
until  no  further  reaction  ensues.  The  pure  vasculose  thus  obtained  pre- 
serves a  light  yellow  tint,  maintaining  the  structure  of  the  original  tissue. 
The  mean  of  several  analyses  of  vasculose  gives  a  compositicl^  corresponding 
to  the  formula,  CggHaoOie. — Amer.  Nat.,  July,  1883;  from  Jour.  Royal  Mic. 
SoG.  for  April,  1883. 
BASIS  OF  THERMO-CHEMISTRY. 
By  L.  Meyer. 
No  simple  connected  theory  of  chemical  change  has  hitherto  been  based 
on  thermo-chemical  investigations,  notwithstanding  their  number  and  the 
trustworthiness  of  the  constants  deduced  from  them ;  indeed  many 
chemists  would  even  consider  that  such  a  generalization  is  for  the  present 
not  ripe  for  discussion.  For  although  many  observations  are  in  direct 
accordance  with  the  mechanical  theory  of  heat,  yet  from  time  to  time  facts 
are  brought  forward  apparently  in  direct  contradiction  to  it ;  as  the  validity 
of  this  theory  cannot  be  doubted,  such  discrepancies  probably  arise  from 
wrong  methods  of  its  application.  According  to  the  author's  opinion,  the 
retention  of  old  and  baseless  hypotheses  hampers  the  framing  of  a  thermo- 
chemical  theory ;  such,  for  example,  is  the  conception  that  the  atoms  are 
particles  of  mass  endowed  with  a  power  of  attraction  through  space, 
although  it  is  at  least  highly  probable  that  attraction,  as  we  conceive  it,  is 
produced  by  a  certain  movement  of  smaller  particles,  arising  from  pressure 
or  impact.  The  satisfaction  of  these  attractions  or  affinities  is  not  then 
correlated  with  a  conversion  of  potential  into  kinetic  energy,  but  the  com- 
binations and  also  the  separations  ot  the  affinities  are  merely  a  conversion 
of  one  form  of  kinetic  energy  inm  another.    Again,  it  is  often  tacitly 
