498 Scientific Proceedings, Royal Dublin Society. 
of each substance the signs - —- 7 or © are placed under its 
formula or symbol to indicate the solid, liquid, gaseous, or 
dissolved states, after the manner of the vowel points in Hebrew. 
Tf the solution be other than a dilute aqueous one, an asterisk or 
other sign is used with a footnote to this effect, and if the solution 
be saturated the sign © is used, thus: —&H.0, €H.0, 60.0 
indicate the heat of formation of water in the solid, liquid, and 
gaseous states, respectively.’ 
In all cases where the energy under consideration is that of 
the formation of the substance in its normal condition at 15° C. 
from its elements in their normal condition at 15° C., it is indicated 
simply by affixing the evolved energy sign to the ordinary chemical 
formula of the substance, which is understood to be present in its 
molecular proportion in grams, and the signs for’ the solid liquid 
and gaseous states are omitted. 
If the final state be other than the normal condition at 15° C., 
the proper sign must be used, and the temperature will be under- 
stood to be that of the transition from this state to the one nearest 
the normal. Thus 
ECO; — 00 ike 
indicates the heats of formation of solid CO, at its melting point 
from its elements in their normal condition at 15° C. 
Tf the initial state be other than the elements in their normal 
condition at 15° C., it is necessary to write the expression in full, 
thus :— ICl } 
E csi 9-8K°. 
Or preferably expand it in the equation form as will be shown 
later. Ii the temperature be other than 15° C., or the melting or 
boiling point as above explained, or if the pressure be other than 
the normal, this should be indicated at the beginning or by placing 
an asterisk under the formula referring to a footnote, but this is 
very seldom required. 
1 These signs may be conveniently remembered as follows :— 
- Solid, the most coherent form of matter. 
— Lnquid, indicated by its horizontal surface. 
7 Gas, tends to expand in three directions. 
° Solution, substance in a surrounding medium. 
© Saturated solution, maximum solid present. 
