2  t  f)  AVr/;'/"-,  ■  e  (  Aai-  Jour-  l-'hariu. 
J1U  OieWS.  {       June,  1^90. 
nected  with  the  reagents  used  in  chemical  analysis.  The  aim  of  the  work,  as 
is  well  expressed  by  its  title,  is  to  give  an  account  of  the  various  uses  to  which 
the  different  reagents  are  applied,  to  prove  their  purity  and  to  show  the  man- 
ner in  which  they  may  be  prepared.  It  will  thus  serve  as  a  supplement  to  the 
various  manuals  intended  for  the  systematic  instruction  in  anatytical  chemistry, 
and  to  the  larger  works  on  chemical  analysis  used  by  the  professional  analyst. 
The  arrangement  of  the  work  is  alphabetical,  commencing  with  the  various 
acids  and  terminating  with  zinc  and  its  compounds.  The  group  alcohols 
includes  glycerin,  and  under  the  heading  color-reagent?  and  indicators,  those 
-numerous  agents  are  found  which  give  different  color-compounds  with  acids 
and  alkalies,  each  reagent  is  considered  first  as  to  its  uses  ;  next,  the  tests  are 
given,  by  which  its  identity  and  purity  may  be  ascertained,  and  finally  one  or 
more  processes  are  outlined,  by  which  the  reagent  may  be  conveniently  pre- 
pared or  the  commercial  article  purified.  The  various  applications  of  the 
reagents  are  briefly  mentioned  when  they  apply  to  well-known  analytical 
methods.  But  a  fuller  description  is  given  for  processes  of  special  application 
or  less  familiarly  known.  As  an  example  of  the  author's  method  of  treating  the 
•subject,  and  also  to  some  extent  of  the  scope  of  the  work.  We  transcribe  from 
page  175  the  paragraph  referring  to  the  uses  of  resorcin,  which  is  as  follows  : 
Resorcin,  or  Meta-diozy-benzol,  is  a  very  delicate  reagent  for  chloroform, 
iodoform  and  chloral  hydrate.  When  a  small  quantity  of  resorcin  is  dissolved 
in  a  slight  excess  of  potassium  hydrate  solution,  it  produces  an  intense  red  color, 
due  to  the  formation  of  rosolic  acid,  on  heating  it  even  with  traces  of  iodoform 
(Lustgarten)  chloroform  or  chloral  hydrate  {Schwarz).  The  reaction  is  especially 
adapted  to  finding  traces  of  these  substances  in  urine.  Small  amounts  of  ferric 
chloride  may  be  identified  by  this  reagent  by  producing  a  violet  blue  color.  It 
also  serves  for  the  detection  of  saccharin,  Fahlberg  (ortho-sulphamine  benzoic 
anhydride,  or  benzoic  acid  sulphinide,  C6H4  CO.  SO.  NH.),  which  is  now  exten- 
sively used  as  a  substitute  for  sugar  ;  on  addition  of  resorcin  and  a  few  drops  of 
concentrated  sulphuric  acid  to  a  small  amount  of  saccharin  and  heating,  the 
liquid  assumes,  in  succession,  a  yellow,  red  and  then  a  dark  green  color,  while 
SO 2  escapes  with  effervescence.  If,  after  cessation  of  this  effervescence,  the 
liquid  is  made  slightly  alkaline  by  potassium  hydrate,  a  strong  green  fluores- 
cence indicates  the  presence  of  saccharin  {Ira  remsen).  It  is  also  used  for  the 
detection  of  carbohydrates  {Ihl,  modified  by  Molisch),  especially  glucose,  which 
gives  a  red  color  when  brought  together  with  an  alcoholic  solution  of  resorcin 
and  floated  on  concentrated  sulphuric  acid.  By  melting  resorcin  with  sodium 
hydrate  phloroglucin  is  obtained.    Mol.  W.  =  109764. 
The  tests  for  the  same  substance  are  given  in  the  following  :  Resorcin  forms 
small,  colorless  rhombic  prisms,  melting  at  no°C,  subliming  at  276*5°.  It  dis- 
solves in  0*67  parts  of  water  at  I2  5°C.  and  easily  in  alcohol  and  ether.  Its 
aqueous  solution  should  not  form  a  precipitate  with  lead  acetate  (absence  of 
pyrocatechin).  It  should  sublime  without  residue.  The  commercial  article  is 
sufficiently  pure  if  not  browned  by  exposure  to  air  and  light.  If  such  is  the 
case,  it  must  be  carefully  resublimed. 
The  following  paragraph  on  the  preparation  of  resorcin  is  equally  instructive, 
and  the  same  must  be  said  of  the  chapter  on  the  use  of  the  spectroscope,  which 
covers  thirteen  pages  and  is  illustrated,  upon  plates,  with  outlines  of  the 
