228 ANNUAL OF SCIENTIFIC DISCOVERY. 



sity of ordinary quartz boing 2.G. Tridymito, like quartz itself, 

 is hexac^onal, but occurs in very beautiful macles. It is uuiax- 

 iii\. — Bull. Soc. Ch., June, 18G9. 



Beauxitc. — Between Taraon and Antibos in the south of 

 France there exists a valuable and extensive bed of beauxite 

 (hydrate of alumina), which has been used for the manufacture 

 of suli)hate of aluminum. This material has been applied, at the 

 sujrsestion of M. Audouin, for the manufacture of crucibles and 

 fire-bricks, and it was found that the best English, French, and 

 German fire-brick could be melted in crucibles made of beauxite 

 and heated by mineral oils and a blast. — Cosmos. 



Formation of Nitre in Egypt. — A. Ilouzeau. — At Tantah, 

 a town of the Delta of the Nile, the houses are built simply 

 out of the river mud, after mixing it with straw and drying the 

 mass in the sun. Tiiey have little stability, for this reason, and 

 frequently tumble to pieces ; whenever this happens the natives 

 at once proceed to erect another l)uilding of precisely the same 

 character on the same spot. Hence it comes that most buildings 

 are placed on a species of hills, some of which are of considerable 

 age, and that the ground retains both liquid and solid secretions 

 of numerous former generations. The author examined some of 

 these earth-hills, both of old and later creation, especially for the 

 purpose of establishing the particular form in which nitrogen is 

 contained in them. The quantity of the latter appears to be the 

 same in earths of different periods ; that of older generations .670 

 per cent., of later .090 per cent. This was divided in : — 



proving the gradual passage of organic nitrogen into ammonia 

 and nitric acid. — Comptes Bendus, Ixviii., p. 821. 



Testing Antimony for Arsenic. — During the last year, on the oc- 

 casion of the inspection of the apothecaries' shops in Prussia, a 

 quantity of tartar emetic was found to contain arsenic; in conse- 

 quence thereof a vigorous investigation was set on foot by the 

 minister for medical affairs and police. The method adopted for 

 testing for arsenic is as follows : Two grams of the suspected 

 tartar emetic are reduced to a fine powder and dissolved in 4 

 grams of pure chlorhydric acid. A quantity of i)ure chlorhydric 

 acid, at least 30 grams, saturated with sulj)iiuretted hydrogen, is 

 then added, the vessel corked tightly, shaken, and set aside. 

 The sliirhtest trace of arsenic gives rise to a vellow coloration, 

 and very soon after to a perfectly perceptible pure yellow pre- 

 cipitate. — Jahrb.f. Pharm. 



Arsenic in the Soda of Commerce. — Fresenius (Zcitschrift) calls 

 att''ntion to tiie fact that the carbonate of sodium as met with in 

 comnu ree contains arseniate or arsenite of sodium. A sample 

 purporting to be chemically pure, heated with cyanide of ])o- 

 tassium in a stream of carbonic acid, gave distinct traces of a 

 mirror ul' arsenic. Five grams of the same salt gave, when dis- 



