276 Chronicles of'Science. [^pi'il> 



while none could be detected in the Kent water. This observation 

 may probably explain much of the discrepancy of evidence in 

 respect of the action of soft water on lead. 



Professor Tomlinson has advanced a very good explanation of a 

 circumstance which has often been a stumbling-block for students : — 

 Why does hydrochloric acid fume when let out into the air, while 

 ammonia, which has a much stronger attraction for water, does not ? 

 After making several observations of specific gravity, boiling-points, 

 &c.. Professor Tomlinson comes to the conclusion that, although 

 ammoniacal gas and hydrochloric acid gas are greedily absorbed by 

 water, there must be some important differences in the constitution 

 of the respective solutions. The alkaline solution is much lighter 

 than its own bulk of water, whilst the acid solution is much 

 heavier; also the presence of ammoniacal gas in water lowers its 

 boiling-point, while the presence of hydrochloric acid in water has 

 a contrary effect. Hence the mode of combination between ammonia 

 and water must be different from that between hydrochloric acid 

 and water. Tlie one must be a case of simple adhesion, the other 

 of true chemical combination as well as adhesion. Ammonia let oat 

 into moist air simply adheres to the moisture, and increases its 

 volume. Vapour of alcohol, ether, &c., does the same. Now any 

 amount of aqueous vapour that the air can maintain in an invisible, 

 elastic state, at a given temperature, it can maintain with increased 

 effect in the case of ammonia vapour, alcohol vapour, &c. Hence 

 the combination of these vapours with the moisture of the air is 

 necessarily an invisible compound. Hydrochloric acid gas, on the 

 other hand, let out into the air, combines chemically with the 

 moisture, producing condensation or diminution of bulk. Hence 

 the compound is visible, just as the condensation of pure steam in 

 air produces visible vapours. Fuming nitric acid and Nordhausen 

 sulphuric acid are also cases in point. Concentrated nitric acid, 

 exposed to the air, absorbs moisture until it attains the density 

 of 1 "424, when it distils unaltered at a boiling-point of 250°. 



Dr. Carter Moffat has succeeded in fixing on paper the beau- 

 tiful figures which are produced when oils, &c., are allowed to fall 

 drop by drop on a surfiice of pure water, and which Professor 

 Tomlinson has shown to be characteristic of each oil. The method 

 is very simple ; and is, briefly, to obtain a pattern on water, note the 

 time, lay on the paper, glazed side downwards, for an instant, take 

 out, draw through a plate of ink, remove, and wash with water. The 

 process is capable of great extension, and will be valuable to 2)aper- 

 stainers and others. Several books of oJco^jraphs, as these figures 

 are called, have been presented by Dr. ]\Io(liit to different indi- 

 viduals uitercstcd in them, and have elicited cordial approbation. 



According to M. Oser, every time that solutions of sugar fer- 

 ment under the influence of yeast, besides alcohol, a new alkaloid is 



