. 
138 Analyses of Books. [Aue. 
poured into ammonia a white powder falls, which detonates feebly,. 
and affords iodine and a gas not capable of supporting combustion. 
When the acid is coloured the precipitate formed is black, and 
detonates much more loudly. 
Tin and iodine, when combined, form a body possessing acid pro- 
perties, though no hydrionic acid could be detected in it. 4. On 
the action of some compound gases on iodine. It absorbs sul- 
phureted hydrogen and forms a reddish brown fluid. When iodine 
was sublimed in olefiant gas a little reddish brown fluid was formed. 
It produced no change on nitrous gas*nor carbonic oxide; but 
when mixed with carbonic oxide in the gaseous state and exposed 
to the light of the sun, a combination seems to take place. 5. On 
the mode of detecting iodine in combinations, and on certain pro- 
perties of its compound with sodium. The marine productions of 
the Mediterranean contain less of it than the sel de varec. Ashes 
of the ulva, that abounds on the coast of Languedoc, yielded traces 
of it. As did the ashes of the following plants : fucus cartilagineus, 
fucus membranaceus, fucus rubens, fucus filamentosus, ulva_pa- 
vonia, ulva linza. 
The ashes of corralines and sponges exhibited no traees of it. 
Its presence is detected by its property of tarnishing silver, and by 
the red fluid which alkaline leys containing it form with sulphuric 
acid. 
Sir H. Davy conceives it possible that the superiority of bay salt 
in curing fish and meat, may depend upon the presence of this 
substance. He rubbed pieces ef beef with iode and oxiode of 
sodium. They did not putrify. The piece rubbed with the iode 
became brown, soft, and tender; that rubbed with the. oxiede 
hardened considerably and became paler. 
XI. Observations respecting the natural Productions of Saltpetre 
on the Walls of subterraneous and other Buildings. By John Kidd, 
M.D. Professor of Chemistry in Oxford.—The formation of nitre 
upon calcareous stones in certain situations has been long. known, 
and advantage has been taken of it to procure that important salt in 
great quantities; though no satisfactory theory of the formation of 
the salt itself has yet been offered to the public. The present 
paper contains a set of observations on the appearance of an efflo- 
rescence of saltpetre on the walls of the Ashmole laboratory at 
Oxford, a large ground room, sunk below the area of the street, 
The walls are built of Oxford lime-stone, a granular floetz lime- 
stone containing many fragments of shells, of vegetable bodies, 
and composed of 96 carbonate of lime, and 4 of ochrey sand. 
The salt formed was nearly pure, though it contained traces of 
lime and of sulphuric and muriatic acids. What was formed in 
winter contained most lime. The formation of this salt was most 
rapid in frosty weather; it formed slowly, and the quantity even 
diminished in moist weather after it had been deposited. Exclu- 
sion from the air did not preclude the deposition of the salt, though 
it diminished it considerably. 
