VARIETIES. 
375 
paper, silk, leather, &c, Keinsch adopts the following process : — 2 parts of 
solution of copal, 2 parts of that of sandarach, and 4 parts of solution of 
Damara resin (equal parts of resin and absolute alcohol) are mixed with 
half their volume of oil of bergamot or rosemary. This mixture is to be 
evaporated to the thickness of castor oil. If this varnish be then drawn by 
means of a feather or brush over the surface of some water, it will form a 
beautiful iridescent pellicle. This film is now to be applied to the objects 
which are to be rendered iridescent. The vessel in which the water is con- 
tained, on which the pellicle has been produced, must therefore be as large 
as, or larger than, these objects. The water should have about 5 per cent, 
of pure solution of lime added to it ; its temperature should be kept at about 
72°. The objects are dried in the air. — Ibid, from Kunst und Geioerbebl. 
fur Baiern, 1852, p. 165. 
Researches on the Constitution of Organic Acids. By M. Charles Ger- 
hardt. — The experiments described in this communication were instituted 
with the view of establishing a general formula for organic acids, which 
should be to them what the formula for ammonia is to the organic alkalies. 
The author believes that water, the molecule of which he assumes to consist 
of 1 atom of oxygen and 2 atoms of hydrogen, may be taken as the type of 
organic acids, the two atoms of hydrogen being capable of being replaced 
by simple metals, or by complex groups, such as methyle, aethyle, &c. Ke- 
ference is made to the results obtained by Dr. Williamson and M. Chancel, 
tending to prove that alcohol, ether, and their homologues ; represent mole- 
cules of water in which the two atoms of hydrogen are partly or wholly re- 
placed by complex groups ; in accordance with which theory the compound 
formed by replacing 1 atom of hydrogen in alcohol by potassium may be 
considered as the potassium salt of a weak acid, aethylic acid, which gives 
rise to a chloride (hydrochloric ether or chloride of aethyle) when acted upon 
by perchloride of phosphorus. Keference is also made to the experiments 
of Cahours, proving that various organic acids, such as benzoic, nitroben- 
zoic, cuminic, anisic and cinnamic acids, experience similar changes under 
the influence of the same reagent. 
Starting from this point, the author concluded, that, by imitating the well- 
known reaction sethylate of potassium on chloride of aethyle, but substituting 
the corresponding compounds of one of the above mentioned acids for those 
of aethyle, the anhydrous acids ought to be obtained — a result which was 
fully confirmed by experiment. With benzoate of soda and chloride of 
benzoyle the experiment succeeded perfectly well when conducted in the 
following way: — The soda salt was well dried and mixed with an equivalent 
weight of the chloride, and the mixture heated to 130° Cent., when it formed 
a limpid liquid, which at a temperature a few degrees higher underwent 
decomposition, the peculiar smell of the chloride of benzoyle disappearing, 
and chloride of sodium being deposited. The product, suspended in cold 
water, and washed with carbonate of soda, left a white substance without 
