FREE BOOKS

Author's List




PREV.   NEXT  
|<   114   115   116   117   118   119   120   121   122   123   124   125   126   127   128   129   130   131   132   133   134   135   136   137   138  
139   140   141   142   143   144   145   146   147   148   149   150   151   152   153   154   155   156   157   158   159   160   161   162   163   >>   >|  
er and chlorate of potassa were experimented with, in a similar manner, exactly the same results occurred. 398. Whenever the current passed in these cases, there was decomposition of the substances; but the electro-chemical part of this subject I purpose connecting with more general views in a future paper[A]. [A] In 1801, Sir H. Davy knew that "dry nitre, caustic potash, and soda are conductors of galvanism when rendered fluid by a high degree of heat," (Journals of the Royal Institution, 1802, p. 53,) but was not aware of the general law which I have been engaged in developing. It is remarkable, that eleven years after that, he should say, "There are no fluids known except such as contain water, which are capable of being made the medium of connexion between the metal or metals of the voltaic apparatus."--Elements of Chemical Philosophy, p. 169. 399. Other substances, which could not be melted on glass, were fused by the lamp and blowpipe on platina connected with one pole of the battery, and then a wire, connected with the other, dipped into them. In this way chloride of sodium, sulphate of soda, protoxide of lead, mixed carbonates of potash and soda, &c. &c., exhibited exactly the same phenomena as those already described: whilst liquid, they conducted and were decomposed; whilst solid, though very hot, they insulated the battery current even when four troughs were used. 400. Occasionally the substances were contained in small bent tubes of green glass, and when fused, the platina poles introduced, one on each side. In such cases the same general results as those already described were procured; but a further advantage was obtained, namely, that whilst the substance was conducting and suffering decomposition, the final arrangement of the elements could be observed. Thus, iodides of potassium and lead gave iodine at the positive pole, and potassium or lead at the negative pole. Chlorides of lead and silver gave chlorine at the positive, and metals at the negative pole. Nitre and chlorate; of potassa gave oxygen, &c., at the positive, and alkali, or even potassium, at the negative pole. [Illustration] 401. A fourth arrangement was used for substances requiring very high temperatures for their fusion. A platina wire was connected with one pole of the battery; its extremity bent into a small ring, in the manner described by Berzelius, for blowpipe experiments; a little of the salt, glass, or
PREV.   NEXT  
|<   114   115   116   117   118   119   120   121   122   123   124   125   126   127   128   129   130   131   132   133   134   135   136   137   138  
139   140   141   142   143   144   145   146   147   148   149   150   151   152   153   154   155   156   157   158   159   160   161   162   163   >>   >|  



Top keywords:

substances

 

platina

 

general

 
battery
 

connected

 
whilst
 

positive

 

potassium

 

negative

 

arrangement


blowpipe

 

metals

 

potassa

 

potash

 

manner

 
chlorate
 

current

 

results

 
decomposition
 

introduced


troughs

 

Occasionally

 

occurred

 

contained

 

phenomena

 

exhibited

 

electro

 
carbonates
 

liquid

 

passed


procured
 

insulated

 
conducted
 

decomposed

 

Whenever

 

requiring

 
temperatures
 

fourth

 

oxygen

 

alkali


Illustration

 

fusion

 

experiments

 

Berzelius

 
extremity
 

chlorine

 

conducting

 
suffering
 

substance

 

chemical