^""'Dec'im'"''}      Potato  Starch  and  Other  Starches.  597 
a  second  time,  the  combined  contents  of  the  several  tanks  are  shovelled 
into  a  larger  one  which  is  about  28  x  15  feet,  and  6  feet  deep.  This 
is  then  filled  with  clean  water,  and  by  means  of  a  large  beater,  the 
starch  is  stirred  up  and  suspended  in  the  liquid,  giving  it  the  appear- 
ance of  milk,  which  is  then  pumped  into  tanks  24  x  12  feet,  and 
about  5  feet  deep,  where  it  is  again  allowed  to  settle,  taking  about  15 
hours.  After  the  water  has  been  drawn  off,  there  is  generally  a  super- 
ficial layer  of  about  two  inches  consisting  of  fibre,  dirt,  etc.,  which  is 
shovelled  out,  and  thrown  into  a  tank  to  go  through  the  process  again, 
while  the  clear  starch  is  thrown  into  a  mill  and  ground  to  a  fine 
powder,  which  is  then  put  upon  racks  to  dry.  These  drying  racks 
consist  of  a  number  of  layers  (about  16)  of  narrow  strips  of  wood 
about  an  inch  wide,  which  are  arranged  in  such  a  way  that  the  starch 
in  falling  through  is  distributed  equally  over  them.  They  are  kept 
at  a  temperature  of  about  120°  Fahr.  by  means  of  steam,  and  it  takes 
about  20  hours  to  dry  eight  tons.  When  perfectly  dry,  the  racks  are 
tipped,  and  the  starch  falls  into  bags  placed  in  suitable  positions. 
A  sample  of  the  starch  thus  prepared,  was  examined,  and  the  result 
of  my  investigations  is  given  in  the  table  below. 
Six  samples  of  starch  were  purchased  in  Philadelphia,  and  a  quali- 
tative examination  was  made  for  the  purpose  of  comparing  them. 
They  fairly  represent  the  commercial  starch,  being  of  various  qualities, 
and  bought  in  different  sections  of  the  city. 
Ash. 
Moisture. 
Soluble 
M  atter . 
Reaction. 
Variety  of 
Staroh. 
1 
2 
3 
4 
5 
6 
.275  per  cent. 
.4->2  per  cent. 
.439  per  cent. 
.641  per  cent. 
.060  per  cent. 
.553  per  cent. 
.386  per  cent. 
15.225  per  cent. 
13.347  per  cent. 
10.907  per  cent. 
11.413  per  cent. 
12.452  per  cent. 
.200  per  cent. 
.380  per  cent. 
.560  per  cent. 
.560  per  cent. 
.200  per  cent. 
Neutral. 
Neutral. 
Neutral. 
Alkaline. 
Alkaline. 
Potato. 
Corn. 
Corn. 
Corn. 
Wheat. 
Corn. 
7 
Corn. 
The  ash  in  each  case  was  found  to  be  soluble  in  HCl,  with  the  ex- 
ception of  a  slight  residue,  probably  silicates  incorporated  during  the 
washing  process.  On  neutralizing  this  solution  with  NH4  OH,  and 
adding  NH^  HS,  a  black  precipitate  was  formed  in  all  the  samples 
except  No.  6,  due  to  a  trace  of  iron.  No  copper  was  found  in  any 
of  the  specimens. 
The  quantity  of  moisture  varied,  the  potato  starch  (No.  1)  contain- 
