426  REDUCTION  OF  TEMPERATURE  BY  THE  SOLUTION  OF  SALTS. 
Solu 
100 
3 
5  ><!  c 
The  temperature  falls 
Salts. 
^  ^  3 
P  CD 
from 
to 
%  5' 
o-^ 
10 
14 
4-10-8° 
A-  9-4° 
1-4°  C. 
35-8 
36 
12-6 
4-10-1 
2-5 
9-9 
12 
14-7 
4-11-4 
3-0 
90 
14 
10*8 
-1-  7-1 
3-7 
72*3 
75 
13*2 
4-  6-8 
6-4 
20 
12'0 
4-  5-7 
6-8 
Sulphate  magnesia,  cryst.. 
SO- 
85 
11-1 
4-  3-1 
8-0 
SO" 
40 
10-7 
4-  1-6 
91 
15-5 
16 
13-2 
4-  3-0 
10-2 
28-6 
30 
13-2 
4-  0-6 
12-6 
25- 
30 
15-3 
4-  3-2 
12-1 
80- 
85 
10-7 
—  4-7 
15-4 
,  28-2 
30 
13-3 
—  5-1 
18-4 
.,  69- 
75 
13-2 
—  5-3 
18-5 
Hyposulphite  soda,  cryst.. 
..  98- 
110 
10-7 
—  8-0 
18-7 
120- 
140 
10-8 
—11-7 
22-5 
Chloride  calcium,  cryst.... 
,,200- 
250 
10-8 
—12-4 
23-2 
55- 
60 
13-6 
—13-6 
27-2 
Sulphocyanide  ammonium.. 105- 
133 
13-2 
—18-0 
31-2 
Sulphocyanide  potassium. 
..130' 
150 
10-8 
—23-7 
34-5 
The  absolute  quantities  used  were  between  250  and  500  grm. 
water  and  the  requisite  amount  of  salt.  With  smaller  quantities 
than  about  200  grm.  water  the  absorption  of  the  vessel  exerts  a 
marked  influence,  and  experiments  have  also  proved  that  an  in- 
crease of  the  salts  over  the  proportions  given  above  has  a  similar 
influence. 
A  higher  temperature  at  the  beginning  will  produce  a  diiferent 
result  with  those  salts,  the  solubility  of  which  is  considerably  in- 
creased by  a  rise  of  temperature.  On  dissolving  the  necessary 
quantity  of  saltpetre  in  water  of  23*0°  C.  the  temperature  fell  to 
10-2,  a  difi'erence  of  12-8°  against  10-2°,  at  13-2°.  In  describ- 
ing the  results  it  is  necessary  to  give  the  temperature  at  the  be- 
ginning and  end  of  the  experiment,  and  not  merely  the  differ- 
ence. 
A  reduction  of  temperature  below  the  freezing  point  of  the  resp. 
solution  cannot  be  obtained,  but  this  point  may  be  reached.  The 
temperature  of  water  of  0°  C.  on  mixing  with  the  requisite 
amount  of  saltpetre  fell  to  — 2*7°,  crystallized  soda  to  — 2-0°, 
