1878.] 



Supersaturated Saline Solutions. 



123 



the flask. On the 4th and 5th of January the air was still, but dark 

 with a wet fog, accompanied now and then by a small rain, a state of 

 weather which experience had shown to be hopeless as to any nuclear 

 action on the part of the oils ; but on these days drops of phosphorised 

 oil of cajuput, castor-oil, and benzole produced the immediate solidifica- 

 tion of solutions of sodic sulphate and of alum. I may also add that 

 a minute bit of phosphorus was eminently nuclear, and also newly 

 prepared phosphoric acid, whether dry or in aqueous solution. 



(Addendum.) Received January 22, 1878. 



In the series of observations referred to in the above note, the nucleus 

 chiefly employed was oil of cajuput, with occasional reference to castor- 

 oil and benzole. The reason why these three were selected was that 

 after using them, the flasks could be easily cleaned by means of spirits 

 of wine, preparatory to a fresh charge. Another reason was that, by 

 working chiefly with one oil and with solutions of uniform strength, the 

 results were more likely to be comparable than if a number of oils and 

 solutions of different degrees of strength were used. The necessity 

 for clean flasks, as insisted on in my former papers, was abundantly 

 confirmed, especially on days when the wind was northerly and north- 

 easterly. On such occasions, if any traces of the oil used in previous 

 experiments remained in the flasks, the solutions would often solidify 

 in cooling, or on being carried from room to room, although the mouths 

 of the flasks were covered with paper caps or small beakers. The 

 flasks chiefly used have oval bulbs of the capacity of 1^ oz., with stems 

 3 inches in length and about § inch in diameter. Each bulb was filled 

 about half with the filtered solution by means of a small funnel with a 

 long stem, and this was dipped into water after each charge, so as not 

 to soil the neck of the next flask. Each flask was then reboiled until 

 steam issued from the neck, when it was removed from the lamp, its 

 cover was put on, and it was then set upright in a rack to cool. These 

 narrow-necked flasks, if clean, retain the solutions admirably; they 

 may even be left uncovered during many hours, and even days, espe- 

 cially if the necks are inclined towards their support. An uncovered 

 flask has thus remained a fortnight without change. 



Several eminent observers have stated with great persistency that 

 oils have no nuclear action on supersaturated saline solutions ; or if 

 they appear to be active, their activity is due to minute particles of the 

 salt in the air or in the oils themselves. In order to get rid of these 

 supposed nuclear particles, I distilled a number of active essential oils, 

 and found the distillates to be inactive, thus apparently justifying 

 the objection referred to. I also found that ether, methylated spirits 

 of wine, wood spirit, naphtha, benzole, and a few other liquids, were 



