442 
Two  New  Tests  for  Sugar. 
Am.  Jour.  Pharm. 
Sept.,  1886. 
ing  chiefly  of  the  saccharin  of  formose,  C6H10O5,  already  prepared  and 
described  by  Tollens  in  1 884. 
The  condensation  of  formaldehyde  to  a  sugar  nearly  related  to  the 
glucoses  affords  fresh  evidence  in  support  of  v.  Baeyer's  theory  of  as- 
similation in  plants.  Attempts  have  been  made  to  show  that  for- 
maldehyde is  an  intermediate  product  between  carbonic  anhydride 
and  dextrose,  but  without  any  definite  results.  The  author,  therefore, 
intends  to  investigate  the  external  effect  of  formaldehyde  on  plants, 
and  to  ascertain  whether  starch  is  produced.  The  paper  concludes 
with  further  remarks  on  the  relation  of  formaldehyde  to  vegetable 
physiology. — Jour.  Chem.  Soc,  July,  1886,  p.  609.  J.  pr.  Chem., 
321-351. 
TWO  NEW  TESTS  FOR  SUGAR.1 
The  two  reactions  about  to  be  described  are  common  to  cane-sugar, 
milk-sugar,  glucose,  levulose,  and  maltose,  and  to  the  carbohydrates 
and  glucosides  capable  of  yielding  glucose  by  the  action  of  sulphuric 
acid.  They  do  not,  however,  produce  any  result  with  inosite,  man- 
nite,  or  quercite. 
1.  From  one-half  to  two  cubic  centimetres  of  the  suspected  liquid 
are  treated  with  two  drops  of  a  fifteen  or  twenty  per  cent,  alcoholic 
solution  of  alpha-naphthol,  and  the  mixture  is  shaken.  A  slight 
turbidity  results  from  the  precipitation  of  a  little  naphthol ;  sulphuric 
acid  is  then  added  in  quantity  equal  to  or  even  double  the  volume  of 
the  fluid,  and  the  whole  is  briskly  shaken.  In  the  presence  of  sugar 
a  deep  violet  color  is  developed,  and  dilution  with  water  throws  down 
a  violet-blue  precipitate,  soluble  in  alcohol  and  ether  with  a  yellow 
'  color,  or  in  caustic  potash  with  a  golden-yellow  color.  In  order  that 
the  reaction  may  occur  as  described,  the  test  must  be  made  exactly  as 
stated. 
This  test  will  permit  the  detection  of  0*00001  per  cent,  of  sugar, 
and,  with  the  exception  of  vanillin,  anethol,  methyl  salicylate,  and  a 
few  similar  substances,  gives  no  reaction  when  sugar  is  not  present. 
These  substances,  however,  either  produce  the  color  with  sulphuric 
acid  alone,  or  the  precipitate  formed  when  the  violet  solution  is  di- 
1  From  a  communication  to  the  "  Kaiserliche  A,kademieder  Wissenschaften," 
Vienna. 
