30 REPORT — 1865. 



Attention was directed to hexagonal crystals of metallic copper from the mines 

 of Corocoro in Bolivia, out of the red sandstones there ; these were regarded by the 

 author as pseudomorphs, after Arragonite, as although some of them were found to 

 consist of solid metallic copper, yet others on being sawn across were found to con- 

 tain a greater or less nucleus of white carbonate of lime. The formation of these 

 pseudomorphs was explained as having resulted from the action of a solution of 

 protosulphates of copper and iron produced by the oxidation of ordinary copper 

 pyrites on crystals of Arragonite or carbonate of lime. 



Synthetical experiments were related confirmatory of this view, as some crystals 

 of Iceland spar, on being kept some months in a stoppered bottle along with a 

 mixed solution of sulphate of copper and protosulphate of iron, were soon converted 

 superficially into carbonate of copper, which in turn was reduced to metallic cop- 

 per by the deoxidating action of the protosulphate of iron. 



On the Colour of Gold as seen by transmitted Light. 

 By David Forbes, F.U.S., 6fc. 



The author found in several instances where solutions of gold had been precipitated 

 by oxalic acid, that an extremely thin film of gold adhered very pertinaciously to 

 the side of the glass vessel, and that this film, when looked at by transmitted light, 

 was quite blue, and did not at all present the green colour attributed to gold in a 

 fine state of division, as in the common experiments of holding up a thin gold-leaf 

 between the eye and the light. 



He concluded from this that the true colour of gold by transmitted light was 

 blue, and that the green colour usually observed was due to this blue colour being 

 mixed with yellow light reflected from the polished surface of the hammered gold- 

 leaf. 



A most conclusive experiment corroborated this view. In order to get a film of 

 gold infinitely finer than the thinnest gold-leaf, the author took a quantity of the 

 so-called ruby glass of commerce, the colour of which is due to a minute quantity 

 of gold which enters into its composition (amounting to a six-hundreth of a per- 

 centage only), and reduced the gold in this to its metallic state by heating it in an 

 atmosphere of carbonic oxide. The film of gold thus produced, when examined by 

 transmitted light, afforded a most beautiful and pure blue colour without any trace 

 of green whatever. 



On the Constitution of the Acids of the Acetic, Lactic, and Acrylic Scries. By 



Dr. Fkankland, F.R.S., Professor of Chemist/-;/ in the Bayed Institution 



of Great Britain, and in the Royal School of Mines. 



In conjunction with Mr. Duppa, the author had for some time past been 

 engaged in investigating synthetically the constitution of the acids belonging to 

 the acetic, lactic, and acrylic series. They had succeeded in building up the 

 higher members of the acetic series from acetic acid itself, by the substitution of 

 hydrogen in that acid atom for atom, by the alcoholic radicals, methyl, ethyl, &c. 

 Numerous new members of the lactic series had been in like manner constructed 

 from oxalic acid, by the substitution of one atom of oxygen (0 = 16) by two atoms of 

 the alcohol radicals, whilst several members of the acrylic series had been produced 

 from the lactic series by the abstraction of an atom of water from the latter. 



These investigations had led to the following conclusions : — 



1. The acids of all three series are constructed upon the radical type. They are 

 all double radicals, composed of a chlorous and a basylous constituent. 



2. The chlorous constituent is the same in all, and consists of an atom of methyl, 

 in which two atoms of hydrogen are replaced by one of oxygen, and the remaining 

 atom of hvdrogen bv hydroxyl, 



C ]0H. 



It is this chlorous constituent which determines the basicity of these acids, and its 

 repetition twice or thrice in a molecule produces dibasic or tribasic acids. 



3. The basylous constituent is variable, both homologously and heterologously. 



