52 



REPORT — 1855. 



of fluid. The time required for a precipitate to appear was carefully noted down, 

 and also the time which elapsed hefore the liquors were filtered off. The filtrates 

 were then tested to ascertain if any salt of zinc remained in solution. The results 

 obtained are given in the Tables. 



Table I. 



SOaZnO + zHO. 



18 grs. (con- 

 taining 5 grs. 

 of S03) in 

 400 grs. water 



18 grs. in 



400 grs. 



water 



Sulphuric acid. 



2-5 grs. (half the quan- 

 tity of SO^ of the sul- 

 phate) in 50 grs. wa- 

 ter 



59 grs. in 100 grs. water 

 7'5 grs. in 150 grs. water 



10 grs. in 200 grs. water 



12-5 grs. in 250 grs. water 



15 grs. in 300 grs. water 



(or 3 equivalents) ... 



Water. Time when preci- 

 grs.* pitate appeared. 



1050 



1000 

 950 



900 



850 



800 



The precipi- 

 tate appeared in 

 all cases in the 

 space of from 3 

 to 10 minutes 

 after the satura- 

 tion of the li- 

 quor with HS. 

 Rapidity of cur- 

 rent has in- 

 fluence. 



Time of 

 passing 



HS 

 through 

 liquor. 



4 hours 



4 hours 

 4 hours 



6 hours 



6 hours 



6 hours 



Precipitation 

 complete. 



f A trace of zinc 

 [ not precipitated 

 ■] The greatest part 

 >• of the zinc preci 

 J pitated. 



Mr. Calvert also made another series of experiments in which he employed weaker 

 solutions, viz. diluting with twice their bulk of water similar solutions to those obtained 

 in the above table, and these are the results obtained : — 



Tablk II. 



6a, 



S03ZnO + 7HO. 



18 grs. in 



1-500 grs. < 



water 



Sulphuric acid. 



10 grs. in 100 grs. water 

 12-5 grs. in 125 grs. water 



15 grs. in 150 grs. water 



Water. 



grs.t 



3900 

 3875 



3850 



Time when 

 precipitate 

 appeared. 



After a few 



minutes 



ditto 



ditto 



Time of 



passing 



HS 



through 

 liquor. 



5 hours 

 5 hours 



5 hours 



All precipitated. 



(-Almost all precipi- 



i tated; after 12 hours' 



I standing, complete. 



f Precipitate not com- 

 plete even after 12 



; hours' standing; the 

 quantity not precip. 



Lwas considerable. 



It will be observed, in perusing the above tables, that zinc is freely and generally 

 completely precipitated from its combination with sulphuric acid, even in liquors 

 containing a great excess of sulphuric acid, or from 3 to 4 times as much free sulphuric 

 acid as existed in the quantity of salt used. 



Mr. Calvert also thought it advisable to make a series of experiments, employing 

 chloride of zinc, and adding to it submultiple or multiple quantities of hydrochloric 

 acid; and these were the results obtained. 



The required amounts of acid were calculated by employing a quantity of acid con- 

 taining a given proportion of chlorine. 



* The quantity of water in column 3 is such, that when added to the quantity of water in 

 columns 1 and 2, the sum is always 1500 grains, 

 t Total quantity employed, 4500 grains. 



