114 
Solubility  of  Calcic  Hydrate. 
<  Am.  Jour.  Pharos 
\       Feb.,  1884. 
The  U.  S.  Pharmacopoeia  states  that  "  the  alkaline  reaction  of  the 
liquid  entirely  disappears  after  it  has  been  saturated  with  carbonic  acid 
gas,  and  the  excess  of  the  latter  has  been  expelled  by  boiling  (abs.  of 
alkalies  or  their  carbonates)."  This,  however,  is  not  so ;  the  liquid 
after  boiling  is  still  alkaline,  though  of  course  not  to  any  large  extent, 
and  the  test  as  it  stands  is  therefore  worthless. 
The  other  hypothesis  is  similar  in  principle  to  that  just  explained. 
If  after  nitration  the  lime  water  is  kept  in  vessels  of  too  large  a  capa- 
city, or  in  unstoppered  bottles,  calcic  carbonate  is  rapidly  deposited. 
Even  when  most  carefully  preserved,  this  takes  place  to  a  certain 
extent,  the  coating  of  carbonate  inside  the  shop  bottles  being  a  fami- 
liar sight  to  all  of  us.  This  is  of  itself  quite  sufficient  to  account  for 
occasional  jnferior  specimens,  and  it  will  be  remembered  was  the 
defence  urged  at  a  recent  trial ;  but  if  there  is  reason  to  suspect  that 
the  lime  water  is  habitually  weak,  the  explanation  would  probably  be 
found  in  the  fact  that  the  stock  of  lime  was  for  the  most  part  in  the 
form  of  carbonate. 
It  is  difficult  to  understand  why  the  presence  of  carbonate  should 
prevent  the  solution  of  the  hydrate  when  the  latter  is  present  in  suffi- 
cient quantity  to  saturate  the  water,  but  I  have  repeatedly  proved  that 
it  does  so,  whatever  be  the  explanation  of  the  fact. 
Solubility  of  Calcic  Hydrate  at  Different  Temperatures. 
Temper- 
ature. 
Deg's  C. 
Expressed 
in  grains 
CaO  per 
fluid- 
ounce. 
Expressed 
as  1  part 
CaO  in 
parts 
water. 
Expressed 
as  parts 
CaO  in  100 
parts 
water. 
Temper- 
ature. 
Deg's  C. 
Expressed 
in  grains 
CaO  per 
fluid- 
ounce. 
Expressed 
as  1  part 
CaO  in 
parts 
water. 
Expressed 
as  parts 
CaO  in  100 
parts 
water. 
0 
•576 
759 
•131 
55 
•396 
1,104 
•09 
5 
•572 
764 
•130 
60 
•385 
1,136 
•088 
10 
•568 
770 
•129 
65 
•362 
1,208 
•082 
15 
•561 
779 
•128 
70 
•354 
1,235 
•08 
20 
•553 
791 
•126 
75 
•333 
1,313 
•076 
25 
•526 
831 
•120 
80 
•321 
1,362 
•073 
30 
•507 
862 
•116 
85" 
•315 
1,388 
•072 
35 
•481 
909 
•109 
90 
•277 
1,579 
•063 
40 
•469 
932 
•107 
95 
•265 
1,650 
•06 
45 
•444 
985 
•101 
99 
•265 
1,650 
•06 
50 
•429 
1,019 
•098 
— Phar.  Jour,  and  Trans.,  Dec.  29,  1883. 
