DURING METALLIC SUBSTITUTIONS. 
toi 
In this case the numbers obtained with the nitrate agree with the others. Hence 
we have for the heat developed during the precipitation of 
C. F. 
1 grm. silver by copper . . . . 161° or 290° 
1 equiv. silver by copper . . . 2176° or 3917°. 
Salts of Lead with Zinc. 
Acetate of Lead and Zinc. — The precipitation of lead from its solutions by metallic 
zinc is difficult to complete in a short space of time. A large excess of zinc (8 grms.) 
was required and four minutes of agitation. The results on this account are only 
approximations. The solution weighed 130 grms. and contained 1*305 grm. oxide 
of lead. The thermal equivalent of the whole was 136*0 grms. water. 
I. Air 17°’8. Increment found 1°*63, corrected 1°*60. 
II. Air 16° 5. Increment found 1°*68, corrected 1°*65. 
I. II. — Mean. 
180° 185° 182*5°. 
Formiate of Lead and Zinc. — 0*433 grm. of the salt employed gave 0*324 grm. oxide 
of lead. 100 grms. of the solution contained 1*35 grm. of the formiate. 
I. Air 12°*7. Increment found 1°*74, corrected 1°*61. 
I. 
181°*5 
Hence we have for the heat evolved during the precipitation of 
C. F. 
1 grm. lead by zinc 182° or 327° 
1 equiv. lead by zinc 2357° or 4243°. 
Salts of Mercury with Zinc. 
Chloride of Mercury and Zinc: — This is the only salt of mercury which was 
examined. The result however is sufficient to determine the thermal position of 
mercury among the metals. 100 grms. of a solution containing T240 grm. chloride 
of mercury were taken. The thermal value of the whole was 106*4 grms. water. 
In this case no further development of heat occurred after the precipitation was com- 
pleted, nor was there any disengagement of hydrogen gas. The excess of zinc, in 
fact, became amalgamated, which effectually prevented both oxidation and voltaic 
action. 
I. Air 16°*6. Increment found 2°*86, corrected 2°*86. 
II. Air 16°*5. Increment found 2°*85, corrected 2°*88. 
III. Air 16°*4. Increment found 2°*88, corrected 2°*88. 
I. 
332° 
II. 
334 
III. 
334’ 
Mean. 
333°. 
