COPPER, SILVER, AND GOLD 435 



chloride, he took pure rock salt, containing only a small quantity of 

 magnesium and calcium compounds and a small amount of potassium 

 salts. This salt was dissolved in water, and the saturated solution 

 evaporated by boiling. The sodium chloride separated out during the 

 boiling, and the mother liquor containing the impurities was poured 

 off. Alcohol of 65 p.c. strength and platinic chloride were added 

 to the resultant salt, in order to precipitate all the potassium and 

 a certain part of the sodium salts. The resultant alcoholic/ solution, 

 containing the sodium and . platinum chlorides, was then mixed with a 

 solution of pure ammonium chloride in order to remove the platinic 

 chloride. After this precipitation, the solution was evaporated in a 

 platinum retort, and then separate portions of this purified sodium 

 chloride were collected as they crystallised. The same salt was pre- 

 pared from sodium sulphate, tartrate, nitrate, and from the platino- 

 chlpride, in order to have sodium chloride prepared b# different methods 

 and from different sources, and in this manner ten samples of sodium 

 chloride thus prepared were purified and investigated in their relation 

 tK? silver. After being dried, weighed quantities of all ten samples 

 of sodium chloride were dissolved in water and mixed with a solution 

 in nitric acid of a weighed quantity of perfectly pure silver. A 

 slightly greater quantity of silver was taken than would be required 

 for the decomposition of the sodium chloride, arid when, after pour- 

 ing in all the silver solution, the silver chloride had settled, the 

 amount of silver remaining in excess was determined by means of a 

 solution of sodium chloride of known strength. This solution of 

 sodium chloride was added so long as it formed a precipitate. In this 

 manner Stas determined how many parts of sodium chloride corre- 

 spond to 100 parts by weight of silver. The result of ten determina- 

 tions was that for the entire precipitation of 100 parts of silver, 

 from 54-2060 to 54-2093 parts of sodium chloride were required. The 

 difference is so inconsiderable that it has no perceptible influence 

 on the subsequent calculations. The mean of ten experiments was 

 that 100 parts of silver react with 54*2078 parts of sodium chloride. 

 In order to learn from this the relation between the chlorine and 

 silver, it was necessary to determine the quantity of chlorine contained in 

 54-2078 parts of sodium chloride, or, what is the same- thing, the quantity 

 of chlorine which combines with 100 parts of silver. For this purpose 

 Stag made a series of observations on the quantity of silver chloride 

 obtained from 100 parts of silver. Four syntheses were made by him 

 for this purpose. The first synthesis consisted in the formation of 

 silver chloride by the action of chlorine on silver at a red heat. This 

 experiment showed that 100 parts of silver give 132-841, 132-843 and 



