376 Mr. T. J. Herapath on some Combinations of 



of caustic ammonia (I., IV.). It would also appear to be pro- 

 duced when the basic acetate of lead is imperfectly precipitated 

 by biborate of soda (II., V.), or when an acid solution of either 

 of the subsequently described borates is supersaturated by 

 strong liquor a mmonice (III., VI.). 



It is a heavy, white, amorphous powder, which is almost 

 insoluble in water, both hot and cold. It is perfectly inso- 

 luble in alcohol. It dissolves with great facility in dilute nitric 

 acid, even when cold, and likewise in boiling acetic acid ; from 

 these solutions it may be again precipitated unaltered, by 

 adding a large excess of ammonia. It is easily decomposed 

 by sulphuric and hydrochloric acids, and likewise by a boil- 

 ing solution of caustic potash or soda. Before the blowpipe, 

 it intumesces, gives off water, and becomes dark in colour ; 

 and at a low red heat fuses into a clear colourless glass, which 

 possesses a specific gravity of .5*5984<, at 5Q° F., and is softer 

 than common flint-glass. Heated to redness on charcoal, it 

 is partially reduced, and the fused mass contains numerous 

 globules of metallic lead. 



The following are the results of my analysis of the hydrated 

 salt, after it had been exposed to a temperature of about 212°F., 

 in a Liebig's drying-tube, for three or four hours, 



I. 9*2 grains were heated to redness in a platina capsule ; 

 loss =0-598 gr. = 6-5000 per cent. 



II. 10 grs., treated as before, lost 0-683 gr. in weight 

 = 6-8300 j)er cent. 



III. H-Ol grs. lost 0-684 gr. in weight=6-2125 per cent. 



IV. 10 grs. were dissolved in dilute nitric acid, and the 

 solution precipitated by an excess of diluted sulphuric acid; 

 PbO, SO^ 9-77 grs. = PbO 7-198 grs. = 71-9800 per cent. 



V. 20 grs. gave of PbO, SO^ 19-80 grs. = PbO 14-578 grs. 

 = 72-8900 per cent. 



VI. 20 grs. gave of PbO, SO^ 19-03 grs. = PbO 14-0221 

 grs. = 70- 11 05 per cent. 



I. II. III. IV. V. VI. Mean. 



HO . 65000 6-8300 62125 ... ... ... 6-5141 



PbO . ... 71-9800 72-8900 70-1105 71-6601 



BO^ . .. ... ... 21-8258 



Now, if we consider the composition of this hydrated salt to 

 be represented by the formula PbO, BO'^-f HO, it ought to 

 contain — 



Water .... 1 9 or 5-7692 per cent. 



Oxide of lead. . 1 112 ... 71*7939 



Boracic acid . . 1 35 ... 22*4369 

 This salt begins to lose water between 250° and 300° F. ; and 

 by long-continued desiccation at a temperature of from 450° 



