108 DRAININGS. 



from the hartshorn upon heating is pure ammonia; 

 for the liquid hartshorn is nothing else than water, 

 into which a large quantity of ammoniacal air or gas 

 has been introduced, and is thereby held in solution. 

 This ammonia again evaporates, even at low tem- 

 peratures, from the water, and it is from this circum- 

 stance that the hartshorn derives its pungent odor ; 

 if the heat is increased, the evaporation is increased, 

 and for this reason the solution, in order that it may 

 not lose its strength, must be kept in well-stopped 

 phials and in cool situations. Putrid drainings pos- 

 sess the closest resemblance to this liquid, inasmuch 

 as they also are to be regarded as a solution of am- 

 monia in water ; by evaporation, therefore, they will 

 decrease in strength in proportion to the inattention 

 paid to the coolness of their situation and the clos- 

 ing of the receptacles in which they accumulate. 



If two equal quantities of hartshorn are put, one 

 into an open flask, the other into a saucer which is 

 left standing in the air or in the sunshine, it will be 

 found, after one or two days, that the latter has en- 

 tirely, or almost entirely, lost its odor, whereas the 

 sample in the flask still smells strongly ; for the am- 

 monia, on account of the great surface exposed and 

 the inconsiderable depth of the fluid, can evaporate 

 more rapidly from the saucer than from the bottle. 

 Precisely the same difference must also occur when 

 drainings are allowed to collect in a large, shallow 

 puddle ; or, on the other hand, in a deep and gener- 

 ally closed reservoir. By long standing in the pud- 



