ZOOLOGY AND BOTAHY, MICROSCOPY, ET 



mil. 3 ; with a drop of etherial : - -Mlution, 



and then wash with a drop of ether. A reddish tint sho~ - g -- 



in contra-distinction to quartz g --. inch remains colourless. 



2. Apply a drop of 10 p.c. fluoric acid on the _ - Imme ' 

 opacity shows glass rich in earthy or heavy oxides (calcium, barium. 

 lead. zinc, etc.) ; glasses poor in metal give n ty. 



3. Moisi e end of a platinum wire with the reaction proda 

 Xo. 2. and carefully bring it into the Bunsen flame. A transient green 

 illumination show- acid with certaintv : yellow shows sodium. 

 Faiiiy large quantities of potassium are at the same time recognized by 

 the violet tint transmitted through a cobalt-blue glass held in fror 

 the eye. but better by the characteristic line in the red of a pocket 



t - 



i. Apply a drop of dilute sulphuric acid to the reaction product of 

 X . 2. A black coloration shows lead (flint-glass i. in contrast with 

 ieadless glasses which remain colourless. Antimor. . - the well- 

 known orange precipitate. 



Further investigation on the metallic constituents of glass is per- 

 formed in vessels. For this purpose reaction Xo. 2 is repeated, 



minutes are allowed for development. The reaction product is ri: .- 

 with 3 can. of water in a porcelain or platinum cruciple. and mixed with 

 - - much (about O'l grin.) sodium-bicarbonate th ffer- 



Bnee a small residue is left. This is heated for about two minui - 

 until it coagulates. The completeness of the pro - - attained when 

 a drop of the alkaline fluid dots not d-. - :nethyl-blue solution ; 



should this happen, the heating is to be continued. After 1 tang 



decant, wash the precipitate 3 times with 3-5 com. water, and having 



:ed it in the crucible with 10 drops of dilute hydrochloric acid, 

 reduce it in a steam oven at 100° C. to dryness The small resid 



ted with 3 c.cm. of water, to which 2 drops of dilute hydrochloric acid 



en added. The undissolved portion is the silicic acid of the glass, 



and this must be filtered off. The filtrate is a chloride solution ; it 



must be freed, if necessary, by sulphuric acid from lead (or antimony) 



in <: " be available for further investigations. 



5. Place the solution in a test-tube, acidify with a drop of dilute 

 sulphuric acid, and boil up. A heavy white solution is barium. 



6. Treat the solution, filtered if necessary, from Xo. 5 with a drop 

 of potassium ferrocyanide solution. A white slimy precipitate is zinc ; 

 if the precipitate is bluish, there is a trace of iron. 



7. Treat the solution I if necessary i from Xo. 6 with 3 drops 

 of ammonia solution, and heat to boiling. A white flocculent precipitate 



• '.umininm. 



B. Treat the solution sd if necessary'i from Xo. 7 with 1 drop 



salic acid, and warm slowly. A white opacity after 2 min 

 shows calcium. 



9. Treat the solution (filtered if necessary) from No. 8 th 2 irops 

 of sodium phosphate solution. A - formed granular precipitate 



shows magnesium. 



The author has. in another article,* studied the decomposabili: 



' Deutsche Mech. Zeii. (190S) p. 1. 



