and Attached Water, 33 



hydrate in its solidification leaves the liquid from which it 

 separates continuously more aqueous or less aqueous ac- 

 cording as it started from a solution more or less aqueous 

 than itself. The " more " and " less," as here employed, refer 

 of course to intensity, not to quantity, and the change is the 

 analogue of that suffered by electricity when the surface of a 

 conductor alters in size. 



§ 240. Some Applications of the above Property of Triethyl- 

 amine. — It appears from Table XL IX. that one weight of tri- 

 ethylamine with 19 weights of water is a ratio requiring 34° 

 C, or 93 0, 5 F., that is a low blood-heat, to effect its turbidity. 

 A ratio of 1 of ethylamine and 24*76 of water requires 41° 0. 

 or 105 o, 8 F. for the same effect to be produced: this is a fever 

 heat. Accordingly, a few little glass capsules containing so- 

 lutions of the triethylamine of strengths graduated between 

 these two and thereabouts, and containing also a little mer- 

 cury to assist the stirring-up when shaken, may be 

 of use in the diagnosis of fever. The eye may be 

 fastened to a thread or rod, and so introduced be- 

 neath the arm or into the cavities. I have made a 

 series of 9 such capsules, which show turbidity at F. 

 68°-3, 69°-4, 76°-l, 79°'9, 91°'4, 98°-6, 105°'2, lll°-2, 123°-8. 



§ 241. The radiation from an electric arc passing into an 

 8-per-cent. solution will warm it to opacity. Thin strips of 

 variously coloured glass placed in such solutions will deter- 

 mine the opalescence after various time lapses, — the red 

 glass acting the slowest, and the others, speaking broadly, 

 the quicker the shorter the wave-length of the light they 

 transmit. Two of complementary colour, which together ab- 

 sorb all radiation, or a single black one, act the quickest. 

 Coloured glasses placed between the solution and the source of 

 radiation cause opalescence in times which are the longer the 

 shorter are the transmitted wave-lengths. 



A few drops of the solution placed as a thin film between 

 two thin sheets of flat glass, and prevented from evaporation 

 by sulphur-cement around the edges, forms a sensitive plate. 

 The hand placed upon it leaves a white silhouette. The 

 spectrum thrown upon this plate leaves a transient record. 



It is probable that the heat liberated when triethylamine is 

 mixed with water is, if the expression may be allowed, the 

 real image of the heat which on entering the mixture effects 

 separation. They are both equal in quantity to the heat of 

 subcryohydration ; the former being that heat itself. It is a 

 happy circumstance that the temperature at which separation 

 begins within the limits of 20 to 50 per cent, solutions is a 

 usual atmospheric temperature, namely 18°*3 C. (64°*94 F : ). 



Phil. Mag. S. 5. Vol. 18. No. 110. July 1884. D 



