119 



A paper was read, entitled, " Experiments made on a piece of 

 Pena silver, saved from the Lady Charlotte, wrecked on the coast 

 of Ireland in December 1838, as to its capability of holding water." 

 By W. D. Haggard, Esq. Communicated by Sir Henry Ellis, K.H., 

 F.R.S. 



Plata Pena, so called, is silver collected by quicksilver after the 

 ore is pounded ; it is then placed in a mould, and by great force the 

 quicksilver is squeezed out, when it forms a mass, resembling dry 

 mortar, of great porosity. 



Troy Weight. Decrease 

 lbs. oz. dwts. in weight. 



Original weight when taken from the 1 oo m c\ 



j^jQ^ ° ^ 38 10 lbs. oz. dwts. 



One day placed before the fire 37 15 1 9 5 



TWrdday 35 5 1 7 



Fifth day 34 5 5 11 15 



Eighth day 34 2 5 3 



Weight of water 4 9 3 



Increase 



Weight of the piece supposed to be 1 q ^ a o ^" weight, 



qfitedry | 34 2 lbs. oz. dwts. 



First day from the fire 34 3 1 



Third day 34 2 5 2 2 



Fifth dav 34 4 2 1 17 



Eighthday 34 4 9 7 



Gained in water fi'om the air 4 7 



Weight after water had been forced 1 39 i 19 4 9 10 



into it J 



Total weight of water contained in the piece 5 1 17 



A paper was also read, entitled, " On the Application of the Con- 

 version of Chlorates and Nitrates into Chlorides, and of Chlorides 

 into Nitrates, to the determination of several equivalent numbers." 

 By Frederick Penny, Esq. Communicated by H. Hennell, Esq. 

 F.R.S. 



The researches which form the subject of this paper were sug- 

 gested by an inquiry into the most effectual method of ascertaining 

 the quantity of nitrate of potassa existing in crude saltpetre. The 

 author found that by the action of hydrochloric acid the nitrate of 

 potassa was converted into the chloride of potassium; and converse- 

 ly, that the chloride of potassium might, by the proper regulation of 

 the temperature, be reconverted into the nitrate of potassa by the 

 action of nitric acid. These mutual conversions afforded excellent 

 means of determining, with great exactness, the relative equivalent 

 numbers, in the theory of definite proportions, belonging to these 

 salts, and to their respective constituent elements. The author, ac- 

 cordingly, pursued the investigation of these numbers by several suc- 

 cessive steps, of which the details occupy the greater part of the 

 present paper. He first determines the equivalent of chloride of 

 potassium by decomposing chlorate of potassa into oxygen and chlo- 



