Tht  RURAL  NEW. YORKER 
S99 
Simple  Science 
By  Dr.  F.  D.  Crane 
Removing  Water  from  Coal  Tar 
I  have  40  gallons  of  coal  or  gas  tar, 
but  it  is  mixed  with  about  a  gallon  or  two 
of  water.  Do  you  know  of  some  practical 
and  inexpensive  method  of  removing  this 
water?  G.  b. 
Meadow.  Va. 
It  depends  on  what  you  expect  to  do 
with  the  tar  with  the  water  out  of  it. 
Most  such  tar  carries  a  little  water  at 
best.  If  you  can  warm  the  tar  gently  in 
a  thin  layer,  the  water  will  evaporate. 
Preserving  Color  of  Rustic  Fence 
I  have  just  put  up  a  rustic  fence_  of 
cedar  poles.  Is  there  any  wash,  paint, 
oil  or  other  preparation  that  could  be 
applied  to  this  fence  to  preserve  the  at¬ 
tractive  brown  color  of  the  bark?  I  have 
noticed  that  in  most  cases  this  bark  soon 
becomes  a  dirty,  dark  color.  If  its  fresh¬ 
ness  could  be  preserved  two  or  three 
years  longer  it  would  be  a  great  advan¬ 
tage.  11  •  B- 
Stamford,  Conn. 
The  best  we  can  suggest  is  a  coat  of 
boiled  oil  without  pigment,  followed  by  a 
second  coat  into  which  some  good  varnish 
has  been  stirred.  Perhaps  some  reader 
can  suggest  a  better  treatment. 
Purifying  Cistern 
How  may  I  purify  cistern  water?  I 
have  a  new  cistern  and  intend  to  wash  it 
out  well,  then  fill  with  artesian  well  wa¬ 
ter,  in  order  to  get  cool  water  without 
waiting  for  Fall  rains.  I  suppose  this 
water  will  taste  of  the  cement.  How  can 
I  overcome  this?  j.  n.  s. 
Catasauqua,  Pa. 
Only  by  repeated  filling  and  emptying, 
but  a  few  pounds  of  washing  soda  in  one 
of  the  rinse  waters  will  help  some. 
Silvering  a  Mirror 
What  is  the  substance  used  on  the  back 
of  a  mirror,  and  how  is  same  applied  to 
make  mirrors?  J.  N. 
Mt.  Vison,  N.  Y. 
The  older  mirrors  were  backed  by  put¬ 
ting  tinfoil  on  a  smooth  stone  slab,  pour- 
ing  mercury  (quicksilver)  on  it  and  slid¬ 
ing  a  very  clean  sheet  of  glass  over  the 
top.  This  was  then  weighted  and,  after 
the  mercury  and  tin  had  united  and  the 
resulting  amalgam  had  set,  the  glass  was 
lifted  and  the  backing  protected  by  a 
heavy  coat  of  paint.  The  more  modern 
sorts  are  covered  with  a  layer  of  pure  sil¬ 
ver.  The  nitrate  is  treated,  in  water  so¬ 
lution,  with  just  enough  ammonia  to 
nearly  re-dissolve  the  white  cloud  which 
first  forms.  This  is  the  trick,  to  get  that 
precipitate  just  enough  dissolved.  This 
solution  is  then  added  to  a  warm  solu¬ 
tion  of  formaldehyde  or  glucose,  the  lat¬ 
ter  being  more  dependable,  and  the  mix¬ 
ture  poured  on  the  well-cleaned  glass, 
which  has  a  wax  rim  built  up  around  the 
edge,  and  is,  of  course,  set  level,  so  the 
solution  will  be  of  equal  depth  at  all 
points.  The  metallic  silver  is  deposited 
in  a  short  time,  the  solution  that  remains 
poured  off,  the  layer  well,  but  very  gen¬ 
tly.  washed,  allowed  to  dry  and  backed, 
as  before,  with  a  protective  paint. 
Linseed  Oil  on  Raincoat 
My  raincoat  started  to  leak  and  some¬ 
body  advised  me  to  apply  a  coat  of  lin¬ 
seed  oil.  I  have  done  it,  and  the  coat  be¬ 
came  so  hard  and  stiff  that  it  can  almost 
stand  without  support,  and  I  cannot  wear 
it.  I  tried  to  soak  it  in  water,  but  with¬ 
out  results.  Will  you  tell  me  how  I  can 
soften  it  and  make  it  waterproof? 
Freneau,  N.  J.  m.  s. 
Nothing,  at  this  late  date.  Likely  you 
used  boiled  oil  instead  of  raw,  but  maybe 
something  in  the  goods  acted  as  a  “dry¬ 
er.”  or  it  may  be  the  goods  is  rather  thick 
for  an  oilskin.  Boiling  it  in  dilute  soda 
may  help,  .but  the  last  state  of  that  coat 
is  probably  going  to  be  worse  than  the 
first. 
Dyeing  Tanned  Calfskin 
I  have  a  small  calfskin  which  I  would 
like  to  tan  a  dark  brown  or  black,  to 
use  for  a  book  cover.  What  would  you 
recommend  for  a  dye  bath  for  it?  After 
the  dye  bath  I  suppose  the  proceeding 
would  be  about  the  same  as  published  in 
The  R.  N.-Y.  some  time  ago  for  wood¬ 
chuck  skins.  I  wish  to  have  my  Bible 
covered  with  something  durable ;  the  last 
two  I  have  had  seemed  all  right  when  I 
bought  them,  but  soon  wore  through  and 
proved  to  be  only  imitation  leather. 
Brunswick,  Me.  G.  c.  G. 
You  should  plan  to  get  the  skin  well 
tanned  first,  and  then,  if  it  seems  to  need 
more  color,  you  can  dye  it.  The  general 
tanning  methods  already  outlined  should 
work  all  right  on  a  calfskin,  if  it  is  well 
fleshed  and  dehaired  and  then  tanned 
slowly,  in  weak  extracts  at  first,  so  that 
the  inside  tans  as  fast  as  the  outside. 
Beginners  often  use  such  a  strong  extract 
that  the  outside  tans  so  firm  that  the 
extracts  cannot  get  at  the  middle,  which 
is  left  almost  rawhide.  After  tanning,  a 
lot  of  neatsfoot  oil  should  be  well  worked 
in,  and  then,  if  the  color  is  still  too  light, 
a  weak  solution  of  copperas  will  produce 
a  deep  black,  or  the  aniline  dye  called 
“Bismarck  brown”  may  be  used.  The 
whole  skin  is  likely  too  thick  for  a  book 
binding,  and  thinning  it  down  is  quite  a 
trick,  but  it  can  be  done  with  sandpaper. 
Waterproofing  a  Raincoat 
Can  I  get  a  preparation  that  I  can  ap¬ 
ply  to  the  inside  of  a  raincoat?  I  have 
one  that  leaks  and  I  would  like  to  know 
if  I  can  recoat  it  with  something  to  make 
it  good  again.  MRS.  w.  H.  M. 
Middle  Grove,  N.  Y. 
Not  so  far  as  we  know.  The  water¬ 
proofing  process  is  applied  to  the  cloth 
before  it  is  made  up.  Still,  there  are  all 
sorts  of  raincoats,  and  if  you  chance  to 
have  one  of  the  rubberized  variety,  it  is 
possible  that  tube  mending  tissue  would 
stop  a  small  hole. 
Evaporation  in  Closed  Tank 
Will  water  evaporate  in  a  tank,  air 
and  watertight,  when  kept  at  a  tempera¬ 
ture  of  from  100  to  105  or  106  degrees, 
and  at  this  temperature  would  there  be 
any  danger  of  explosion?  L.  G.  B. 
Darien  Center,  N.  Y. 
If  the  tank  were  filled  with  water  it 
certainly  would  not  evaporate,  but  there 
would  be  considerable  pressure  due  to  the 
expanding  water,  which  would  break  a 
rigid  tank.  The  actual  range  of  the  ex¬ 
pansion  is  so  slight  that  a  tank  made  of 
ordinary  materials  would  “give”  a  little 
and  take  up  the  increase  in  bulk.  If  you 
have  an  air  surface  above  the  water, 
this  will  take  up  the  expansion,  and  the 
pressure  on  the  tank  at  that  temperature 
would  be  insignificant.  In  this  latter 
case  there  would  be  some  evaporation, 
just  enough  to  saturate  that  volume  with 
water  vapor  at  that  temperature,  and 
then  the  volumes  of  water  and  air-water 
vapor  would  remain  constant  for  the 
given  temperature. 
Barium  Carbonate  for  Rat  Poison 
How  do  I  use  barium  chloride  for  a 
rat  poison?  F.  J.  d. 
St.  Remy,  N.  Y. 
You  don’t;  you  use  barium  carbonate. 
The  chloride  might  serve  you  if  you  could 
induce  them  to  eat  it,  but  it  has  a  taste. 
The  carbonate  has  no  taste,  and  is  in¬ 
soluble  till  it  reaches  the  rat’s  stomach, 
where  it  is  changed  to  chloride  and  kills 
the  rat.  The  trick  is  to  get  the  rats  into 
eating  a  given  food  in  a  given  place  for  a 
day  or  so,  then  adding  about  five  per  cent 
barium  carbonate  to  this  food.  Then 
change  the  food  and  the  place,  get  the 
survivors  used  to  the  new  food  in  a  new 
place,  and  then  dose  that.  The  barium 
carbonate  is  cheap  enough  wholesale,  only 
a  few  cents  a  pound.  Better  send  to  the 
Department  of  Agriculture  for  the  bulle¬ 
tin,  free,  on  rats.  Remember,  a  rat  eats 
as  much  as  a  hen  each  day,  and  lays  no 
eggs. 
Filtering  Tractor  Oil 
I  have  two  or  three  gallons  of  extra 
heavy  tractor  oil  which  has  a  little  dirt 
in  it,  making  it  unsafe  for  use  in  a  trac¬ 
tor.  Is  there  some  way  I  can  filter  this 
oil  to  remove  the  grit?  If  the  grit  can¬ 
not  be  removed,  would  this  oil  be  suitable 
to  use  for  greasing  harness?  w.  a.  w. 
Evans  Mills,  N.  Y. 
Try  filtering  it  through  an  old  felt  hat, 
or,  if  you  prefer,  a  new  one.  Mineral  oil 
is  not  suitable  for  leather.  Neatsfoot  is 
the  proper  oil  for  harnesses.  If  the  oil 
is  heavy,  warm  it  up  before  filtering. 
WANT  TO  KNOW 
Waterproof  Dressing 
I  had  a  carriage  boot  of  excellent  fab¬ 
ric,  but  the  waterproof  dressing  had  be¬ 
come  worn  off.  I  waterproofed  it  again 
with  one  of  the  dressings  made  for  auto¬ 
mobile  tops,  with  satisfactory  results.  It 
remained  almost  as  soft  and  pliable  as  an 
undressed  fabric.  Unfortunately,  I  can¬ 
not  name  the  dressing.  Some  of  the  dress¬ 
ings  on  the  market  are  hard  when  dry. 
others  soft.  J.  N.  pardee. 
Massachusetts. 
Waterproofing  Cellar  Floor 
I  would  like  to  hear  from  some  of  the 
readers  who  have  had  experience  in  over¬ 
coming  a  springy  bottom  in  cellar,  with 
waterproofing  the  cement,  or  by  any  other 
better  cement.  I  have  a  good  drain.  2  in. 
cement,  and  water  oozes  up  through  ce¬ 
ment,  causing  it  to  be  wet.  H.  c.  D. 
Albion,  N.  Y. 
Turn  ALL  Your  Gram 
into  Money  with,  a 
7 
THRESHER. 
Make  tills  harvest  mean  a  full  profit. 
Clean  threshing — and  tlireshing  at  the  right 
time — will  add  many  dollars  to  your  grain 
income. 
Instead  of  depending  o.  a  custom 
thresher,  with  all  the  uncertainties,  make 
yourself  independent  by  owning  your  own 
individual  Gray  Line  Thresher.  It  threshes 
all  grains,  beans  and  peas  CLEAN — makes 
Tlireshing  a  simple  chore  that  you  can  do 
when  the  grain  is  just  right,  and  when 
you  are  ready. 
Gray  Line  Threshers  are  light,  compact, 
simple  and  require  little  power.  Five  sizes, 
capacities  30  to  120  bu.  oats  per  hour. 
Use  coupon  below  to  secure  catalog  and 
low  price  list. 
A.  W.  Gray’s  Sons,  Inc.,  Poultney,  Vt. 
Gray  Line  Quality 
has  been  known  to 
thousands  of  users  of 
our  wood  saws  and 
Threshers,  since  1840. 
Every  machine  U 
built  by  craftsmen 
who  know  that  Gray 
Line  equipment  must 
be  “built  for  keeps.’’ 
Gray  Line  Wood 
Saws  are  built  for 
lifetime  service — yet 
the  prices  are  very 
moderate.  ASK  FOR 
CATALOG. 
Factory  at  Middletown  Springs,  Vt. 
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Organized  Co-operation 
A  NEW  BOOK 
By  JOHN  J.  DILLON 
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