36 REPORT—1868. 
of phthalic acid from benzol by M. L. Carius. The oxidation of an organic sub- 
stance may therefore give rise to higher compounds during its passages to 
NH,, CO,, and H,0O. 
Ammonia. Carbonic acid. Water. 
The author will examine the isometric lutidine; one or other should give the 
acid with great ease. He believes these bases to be produced by the simultaneous 
action of hydrocyanic acid or ammonia on acetylene at high temperatures, and 
intends investigating their action.} 
On Kekulé’s Model to illustrate Graphic Formule, By J. Dewar. 
The author exhibited to the Section a model devised by Professor Kekulé to 
illustrate the structure of organic compounds. He explained the peculiarity of the 
model consisted in carbon, with its four atomicities, being represented by a small 
sphere, with four equal wire arms joining the centre of the sphere with the angles 
of an imaginary equilateral tetrahedron; the biatomic and triatomic elements by 
two and three arms in a plane passing through the centres of small spheres; the 
lengths of these arms being made so as to join two and three of the extremities of 
the carbon arms. In order to exhibit the facility with which the model could be 
used in lecture illustration, he demonstrated to the Section the structure of a number 
of organic compounds, both fatty and aromatic. He also showed the ease with 
which it could be applied to explain the differences in the isomeric cyanides and 
similar cases. In all cases the model gave elegant symmetrical figures, clearly 
showing the relations of the different groups in the compounds. He afterwards 
referred to certain peculiarities of the model of some importance. The arms 
attached to the individual atoms might be looked upon as unit forces, the length 
of the arms being considered as bearing some relation to their respective magnitudes. 
Now in this model, although the specific atom has its unit values equal, they are not 
the same as the unit values in other atoms. In other words, although oxygen is 
biatomic and can saturate two units of the carbon atom, it is represented as a re- 
sultant and notasasum. ‘This prevents the student from confounding the number 
of units of attacking power, and any comparison between the values of the indi- 
vidual units in different atoms. The author concluded by advocating the judicious 
use of such a model in the tuition of organic chemistry, as a great aid in con- 
veying clear and definite notions on the acknowledged intricate questions of atomi- 
city and chemical structure. 
On the Vapour-tension of Formiate of Eihyl and of Acetate of Methyl. 
By W. Dirt ar. 
The author reports on experiments instituted for determining, by direct compa- 
risons, the difference of the vapour-tensions, at a series of temperatures, of the two 
metameric ethers named. The determinations were made by the statical method, 
and the apparatus constructed so that the two vapours (enclosed in vertical 
glass tubes) pressed against each other through one continuous mass of mercury, 
and that consequently the difference in tension was obtained directly by the mea- 
surement of the difference of level of two menisci, which was effected by means of 
a cathetometer. 
The author, after detailing the methods used for preparing and testing the sub- 
stances operated upon, gives the result of thirty experiments in a table, of which 
the following is an extract :— 
Tension of formiate= 
Tension of acetate = 
Ga NB al Bye ORO 48:6 bbl 69:0 78:95 
f-a=+1535....216 36:1 41:5 52°75 59-2 
The results lead to the conclusion that at temperatures between 18° C. and 80° C. 
the vapour-tension of formiate of ethyl is greater than that of acetate of methyl, 
and that the difference increases with the temperature. 
f pat i° C. in millims. of mereury of 15° C, 
