48 REPORT—1850. 
tained, but the distilled fluid contains a large quantity of hydrocyanic acid. A vola- 
tile base is obtained by supersaturating with potash the residue in the retort, but in 
so small a quantity that it has been as yet impossible to ascertain whether or not it 
may not be a small quantity of unchanged nicotine, although the experiments made 
render that improbable. 
On a Compound of Iodine and Codeine. 
By Tuomas Anverson, M.D., F.R.S.E. 
The author commenced his paper by referring to the constitution of codeine which 
he had determined by his previous investigations, and referred in detail to the com- 
pounds and products of decomposition which had enabied him to fix its formula as 
Cs, Ha NOs. 
The compound of iodine and codeine which formed the special subject of his com- 
munication is obtained by mixing together alcoholic solutions of equal quantities of 
codeine and iodine, and leaving the mixture to spontaneous evaporation, when the 
new compound is deposited in crystals. The compound is insoluble in water, spa- 
ringly soluble in cold alcohol but readily in boiling, and it is again deposited in small 
triangular plates as the solution cools. Its crystalline form has been determined by 
Prof. Haidinger of Vienna, who finds it to belong to the doubly obiique system. The 
crystals have a fine diamond lustre and a deep purple colour by reflected, and ruby- 
red by transmitted light. In powder its colour is cinnamon-brown. 
The analysis of this substance had been attended with considerable difficulty from 
the very large amount of iodine it contains, but the author had been enabled to de- 
termine its formula to be C3. Η.. NO, I. 
Its alcoholic solution is decomposed by sulphuretted hydrogen, and the solution 
contains hydriodate of codeine. Nitrate of silver poured upon the pulverized sub- 
stance immediately produces iodide of silver; but in this way the author found that 
the whole iodine could not be separated, but that the iodide of silver obtained was 
variable in different experiments, aud always fell 13 or 14 per cent. short of the cal- 
culated quantity. 
The optical properties of this substance have been examined by Prof. Haidinger of 
Vienna. When examined with the dichroscopic lens by transmitted light, the ordi- 
nary image is seen of a colour varying according to the thickness of the crystal from 
honey-yellow to blood-red, while the extraordinary image begins with blood-red and 
soon becomes black as the thickness of the crystal increases. By reflected light the 
one image presents a brilliant ultramarine-blue, the other a ruby-red. The former 
of these however varies with the angle of incidence, and passes into violet, and with 
very high angles of incidence into bronze yellow. 
Remarks on some Chemical Facts connected with the Tessellated Pavements 
discovered at Cirencester. By Prof. Buckman, £.L.S., F.GS. 
In this paper it was shown that the materials of which pavements are composed 
are of two kinds :—the first, derived from rocks of the district, and termed natural ; 
the second, composed of clay, fictilia and glass, artificial tesselle. he natural 
tessellae, many of which are so altered by chemical manipulation as to cause them 
to be referred to foreign rocks, consisting of bits of stone from the chalk, oolite, 
lias, and red sandstone formations, were clearly referred to their origin, and the pro- 
cesses by which they were prepared for pavements was pointed out. Thus, a gray 
colour was produced from a cream-coloured oolite, the change of colour being caused 
by a process of roasting. This is dependent upon the fact, that the oolite bed of 
which they are made contains iron and organic matter, the latter of which prevented 
the iron peroxidizing, and thus the gray was due to a protoxide of that metal. 
The artificial tessellee from pottery consist of shades of red and black; the reds 
all being due to a peroxidation of the iron in the clays from which they were made, 
whilst the blacks were the result of baking in “smother furnaces,” as long since 
pointed out by Mr. Artis, so that the carbonaceous matter of the fuel with which the 
baking was effected was prevented from escaping ; and, as he would lead us to infer, the 
black smoke penetrates the clay, and thus blackens it. The author however showed 
