by the mutual reaction of Solid Substances. 207 
loss of heat is sometimes. great, sometimes very slight, accord- 
ing to the amount of liquefaction. Whether moistening will 
take place or not must be decided in nearly every case by 
actual trial, and in the preliminary experiments made with a 
erence to this point 1 have mixed the substances in a wedg- 
wood morta 
From a large number of trials the following conclusions have 
been draw 
1 t is necessary to eo hinccalgen that one of the 
— substances used should be 
It is not necessary that ay solid should be a salt. 
Heinesen sometimes follows the. mixing of a salt with an 
acid, a salt with a base, or a base with an a 
Hx.—Calcium chloride (CaCl, . 6H,O) with es he ae (c HO O- 
Sodium sulphate (Na,SO.. 10H O) with potas. h te (KOH). 
Potassium hydrat e (KOH) with tartari¢ acid (C. o7 
3. As when in the case of liquids, metathesis will take place 
if a compound insoluble in the menstrnum can be formed, so 
with solids, if such a compound can result, metathesis is prob- 
able with liquefaction. 
4. If, by mixing two salts, an insoluble compound is pro- 
duced, a mixture of two others like the new ones formed will 
not, as a general thing, be attended by liquefaction. 
. When no insoluble compound is formed four bodies are 
probably contained in the product, metathesis being partial ; 
for it is sometimes observed that liquefaction seems equally 
marked whether the two original salts are mixed or the two 
bodies formed by their interchange. 
6. The rule among liquids in regard to weak and strong acids 
and bases seems to prevail with solids also, their action tend- 
ing to promote or impede liquefaction. 
en, by the admixture of two salts, oxydation or reduc- 
tion can take place, there is again probability of liquefaction. 
Fe.—SnCl, . - 2H, O with HgCl, liquefied. 
mH. * 
Fe e,Cl,. 
« « CuCl 2H | « 
“ “. © POL, no liquefaction. 
In the last no change by reduction is possible. 
A new substance.—A notable exception to the rule men- 
tioned above, that one salt at least should be hydrated, is that 
of AgNO, mixed with HgCl,. When these are rubbed to. 
gether there is decided moistening, which would seem to Osa 
that there is such a body as anhydrous nitrate of mereur 
liquid at ordinary temperatures. On adding water a me resi- 
due of silver chloride is observe 
