470 Messrs. Wohler and Liebig on 



planes yields common light by reflexion. A truncated hollow 

 cone, the smaller circular section of which was about fourteen 

 lines in diameter, and the larger seventeen lines, was ground 

 into a glass plate, four lines in thickness and three inches in 

 diameter. The lowermost surfaces of the glass were rough- 

 ened at the margin of the circular section and blackened, and 

 the larger circular section was covered with a glass plate, upon 

 which a circular piece of tin-foil was pasted, so that its centi-e 

 coincided with the axis of the truncated cone. The angle of 

 the cone at the apex amounted to 70° 50'. When this appa- 

 ratus is tur;ied towards the sun, so that the rays fall at right 

 angles to the base of the cone, they enter the annular space 

 between the tin-foil and the dark coating of the sheath, and 

 arrive at the reflecting surface of the hollow cone at an angle 

 of 35° 25', thus becoming polarized in all the planes of re- 

 flexion, and after reflexion, crossing at one point of the axis. 

 In the apparatus made by CErtling, this point was exactly in 

 the plane of the smaller aperture of the cone, and was visible 

 when received upon the surface of a piece of white paper 

 placed there. As the polarized light would be depolarized 

 on account of the depolarizing action of this rough surface, it 

 could only be determined that it was unpolarized. This was 

 effected by polarizing the light incident upon the cone by 

 means of an inserted glass plate, and introducing a plate of 

 mica between the inserted glass plate and the cone. The 

 point remained colourless. 



LXXIV. On Thialdine and Selenaldine, two new artificial 

 organic bases. By Wohler and Liebig. Communicated 

 by Dr. A. W. Hofmann*. 



1. Thialdine. 

 'T^HE peculiar deportment of hydrated cyanic acid vrith al- 

 -■- dehyde, which gives rise to a new acid containing the 

 elements of aldehydite of ammonia and hydrated cyanic acid, 

 induced us to study the action of some other substances on 

 aldehyde and aldehydite of ammonia. 



The most interesting product which we ^obtained along 

 with others, is a new organic alkali free from oxygen, and 

 containing carbon and hydrogen in the same proportions as 

 acetic acid, combined with sulphur and the elements of sul- 

 phide of ammonium. This substance, which we call thial- 

 dine f , is highly remarkable from its composition, and we have 

 no doubt that the method which led to its discovery, when 

 applied to other compounds analogous to aldehyde and alde- 

 hydite of ammonia, will yield a long series of new and inter- 



* Communicated by the Chemical Society ; having been read January 4, 

 1847. + Contracted from Oelov and aldehyde. 



