606 sciENTiFtc HF'Cord Von ISU. 



The tanli contained 4.48 grains of zinc carbonate per gallon, with a 

 trace of iron and no lead. Water from the pipe gave 4.29 grains of 

 zinc carbonate per gallon and a trace of iron. 



It is evident, then, when the dangerous nature of zinc as a poison is 

 taken into consideration, that the use of zinc-coated vessels in connec- 

 tion with water or any food-liquid should be avoided. 



Ammonium Fluoride as a Blowpipe Reagent, by Prof. N. W. Lord.— The 

 author recommends ammonium fluoride as a substitute for hydro-potas- 

 sium suli)hate and fluor-spar in developing flame colorations. It has 

 the advantages of being free from fixed alkali and of being easily ap- 

 plied. For testing feldspar or similar silicates a little of the powdered 

 mineral is mixed with ammonium fluoride, placed on a piece of platinum, 

 and moistened with sulphuric acid ; the mixture is gently warmed, 

 taken upon a loop of platinum wire, and tested in the flame of a Bunsen 

 burner or of the blowpipe. The alkali flame is nearly as well shown 

 as with the pure salts. A slight change in treatment renders the re- 

 agent very useful in detecting boron. A high heat must be avoided. 

 The delicacy of the reaction is surprising. {Engineering and Mining 

 Journal.) 



The Reversion of Phosphoric Acid has been further investigated by 

 Thouias S. Gladding. In a previous paper he showed that commercial 

 superphosphates contain the reverted phosphoric acid in three forms — 

 combined with lime, with iron, and with alumina. The artificially pre- 

 l)ared phosphate of lime (whether dicalcic or tricalcic form) is, under 

 given conditions, wholly soluble in a neutral solntion of citrate of am- 

 monia at the temperature of 40° C, while the iron and alumina phos- 

 phates treated in the same way become largely insoluble. The citrate 

 of ammonia solution dissolves every form of reverted phosphate at a 

 temperature of 05° (150° F.), and hence should be used at this tempera- 

 ture. These points are fully sustained in the present publication by ad- 

 ditional experiments, and the investigation is extended to a considera- 

 tion of the reversion of soluble phosphates in artificial and natural soils. 



The author recommends the following method of analysis of super- 

 phosphates, based on the priucii)les stated: 



(a) Preparation of Sample. — Pass the sample through a twelve-mesh 

 sieve. If too wet, a portion must be air dried and then sifted, and an 

 allowance made by calculation for loss of moisture. 



(h) Determination of Moisture. — Dry 5 or 10 grams at 100° C. 



(c) Determination of Total Phosphoric Acid. — Weigh 2 grams, brush 

 into a 200 c. c. flask, add 50 c. c. nitric acid, together with several c. c. HCl 

 when working with difficulty soluble iron and alumina phosphates. 

 Boil gently for fifteen minutes, cool, fill to mark, mix, filter through a 

 dry filter-paper into a dry receiver, take 50 c. c. of filtrate, place in a 

 beaker, add 25 c. c. concentrated ammonia, then nitric acid to acidity. 

 To the hot liquid add molybdic solution, let stand for one hour at about 



