[11] With buttons poor in silver the lowering of the temperature at this stage is not a matter of importance.
[12] 100 grams of the lead, or of its oxide, will contain from 1.5 to 2.5 milligrams.
[13] Still the precautions of having cupels well made from bone ash in fine powder, and of working the cupellation at as low a temperature as possible are very proper ones, provided they are not carried to an absurd excess.
[14] Be careful to remove the crucible before taking the bottle out of the basin of water; if this is not done the chloride may be washed out of it.
[15] 1 c.c. of this dilute acid will precipitate 8 or 9 milligrams of silver.
[16] Chlorides interfere not merely by removing silver as insoluble silver chloride, but also by making it difficult to get a good finishing point, owing to the silver chloride removing the colour from the reddened solution.
[17] These results were obtained when using ammonium sulphocyanate, and cannot be explained by the presence of such impurities as chlorides, &c.
[18] Multiply the standard by 1000, and dilute 100 c.c. of the standard solution to the resulting number of c.c. Thus, with a solution of a standard .495, dilute 100 c.c. to 495 c.c., using, of course, distilled water.
[19] HNa2AsO4 + 3AgNO3 = Ag3AsO4 + HNO3 + 2NaNO3.
[20]
SiO2 + Na2CO3 = CO2 + Na2SiO3
SiO2 + 2NaHCO3 = 2CO2 + Na2SiO3 + H2O.