336 Messrs. M. M. Pattison Mnir and S. Sugiura on 



If tlie results thus obtained for tlic five metals silver, pla- 

 tinum, copper, gold, and aluminium be assumed to hold for 

 metals in general, then the results of this investigation may 

 be summed up as follows : — 



In a circuit consisting of two different metcds a photoelectric 

 current is generated ivhenever the tico junctions are e.iyosed to 

 luminous radiation of diff'erent intensities. 



When the same junction is exposed in one case to an increase 

 of temperature and in another to a more intense illumination, 

 the thermoelectric and j^hotoelectric currents resp)ectively gene- 

 rated in these cases are opposed to each other in direction, 



XLVI. On Essential Oil of Sage. By M. M. Pattison 

 MuiR, F.R.S.E., Assistant Lecturer on Chemistry, and 

 S. Sugiura, Chemical Stude7it, in The Owens College^. 



1. "TT^SSENTIAL oil of sage is obtained by distilling sage 

 -L^ {Salvia officinalis^ with w^ater. The oil upon which 

 we have worked was procured from Messrs. Wright, Layman, 

 and Umney, of London. It was by them believed to be a 

 genuine specimen. We were unfortunately unable to ascer- 

 tain the age of the sample. 



2. The oil was of a yellowish-brown colour, without any 

 shade of green. The smell was intensely sage-like ; the tasto 

 was hot and burning ; the reaction was neutral. The oil did 

 not become resinous, nor did it deposit solid matter on stand- 

 ing in a loosely covered vessel for some months ; the reaction 

 remained neutral. 



The oil readily absorbs oxygen from the air ; about 80 

 cubic centims. of the sample was allowed to stand in an 

 inverted tube containing air, and placed in sunshine. After 

 two days, the level of the oil in the tube showed that the 

 oxygen (about 4 cubic centims.) contained in the confined 

 air had been entirely removed. On testing the oil with paper 

 soaked in starch-paste and potassium iodide, a blue colora- 

 tion was produced, but only after some time. 



Concentrated nitric acid acts most energetically upon sage- 

 oil, with the production of a red semiresinous body: this 

 action is explosive in its violence if the oil and acid be shaken 

 together. 



Strong sulphuric acid causes the production of a brownish- 

 red semiviscid mass ; by this action much heat is developed, 

 and sulphur dioxide is evolved. If the semisolid mass be 



* Read before tlie British. Pkarmaceutical Conference, Glasgow Meet- 

 ing, 187G ; and Plymoutli Meeting, 1877. Communicated by tlie 

 Authors. 



