25 



legler's improved process. 



Legler lias improved the process described in the following way 

 (Clieiiiiker-Zeituiig, vol. 19, p. 17G3) : 



Fifty grams of the sample are thoroughly dried in a porcelain dish and with the 

 ilame of a gas lamp burned from above until thoroughly carbonized, so that the car- 

 bonaceous mass can be easily rubbed to a fine powder, an operation which can be 

 conducted in the dish in which the drying takes place. The fiuely divided carbon is 

 then extracted Avith hydrochloric acid at a boiling temperature in covered beakers, 

 the solution diluted, filtered, and washed. To the filtrate an excess of ammonia 

 is added and it is brought to a given volume. In an aliquot part of the filtrate, 

 after the addition of acetic acid in slight excess, the zinc is precipitated with hydro- 

 gen sulphide and the excess of this gas removed by boiling. The zinc sulphide 

 is then separated by filtration, dissolved and freed from iron, and finally ignited and 

 weighed in the manner given above. In 100 grams of substance Legler found the 

 following quantities of zinc: In three samples, from 40 to GO milligrams of zinc; in 

 one sample, from 20 to 30 milligrams; in six samples, from 10 to 20 milligrams; in 

 fourteen samples, from 5 to 10 milligrams; in eleven samples, from 1 to 5 milligrams; 

 in four samples, 1 milligram; in sixteen samples, none. 



A comparison of the carbonizing method above described with the oxi- 

 dation method, depending upon the use of potassium chlorate, shosved 

 that the two gave practically identical results. The great simplicity of 

 the carbonizing method gives it, therefore, a decided advantage over the 

 older method. At the temperature required for the carbonization there 

 is no danger whatever of loss of zinc by volatilization. 



filsinger's method. 

 According to Filsinger (Chemiker-Zeitung, 1894, vol. 18, p. 1239) — 



It is not absolutely necessary to destroy the organic matter entirely before extract- 

 ing the zinc, but under certain circumstances the hydrochloric acid extract of the 

 organic matter can be used directly. In this case the hj-drochloric acid is neutral- 

 ized with soda lye, acetic acid added, and the solution treated directly with hydro- 

 gen sulphide. The precipitation of the zinc in this case is somewhat hindered by the 

 organic materials which have entered into solution, but the precipitation will take 

 place completely, especially if the solution when saturated with hydrogen sulphide 

 be allowed to stand for some time. A quicker and safer method, however, consists in 

 completely destroying the organic matter of the sample, say 50 grams, by treatment 

 with hydrochloric acid and potassium chlorate. 



METHODS OF ANALYSES EMPLOYED IN THE LABORATORY OF THE 

 DIVISION OF CHEMISTRY. 



After a careful consideration of the different methods of analyses 

 proposed, the method about to be described was adopted by the Divi- 

 sion of Chemistry for the work of analysis of the samples collected. 

 The analytical work for the determination of zinc was carried out by 

 Mr. K. P. McElro}^ and for moisture and ash by Mr. Oma Oarr. 



