182 Analyses of Clam and Oyster Shells. 
ANALYSES OF CLAM AND OYSTER SHELLS. 
BY J. H. SALISBURY. 
[Assistant in the Laboratory of Professor Emmons.] 
In the vicinity of the sea coast, and in the neighborhood of 
large towns, the common clam and oyster shells are quite exten- 
sively used by the farmers as a manure. They are sometimes 
thrown upon the land whole, sometimes previously broken into 
fragments, and often burned. As a general rule the latter method 
may be considered preferable to either of the others. 
Soils, however, containing already a sufficient quantity of lime 
for present demands, and where the object is merely to compen- 
sate for the gradual waste, shells unburned may answer quite as 
good a purpose as those which have been burned. When used 
before burning, owing to their compact texture, they are acted 
upon but slowly by the ordinary agents to which they are sub- 
jected, and hence it requires a much larger quantity of them than 
of burned shells, to exert, in a given time, the same degree of 
influence upon the soil. Unburned, their effects are not materi- 
ally different — throwing aside the small quantity of animal matter 
and soluble salts they contain — from ordinary limestones broken 
equally fine and disposed of in a similar manner. 
Before burning — omitting the moisture — they are made up 
principally of carbonates, with a small quantity of organic matter, 
phosphates, sulphates and chlorides. The process of burning ex- 
pels nearly all of the carbonic acid, organic matter, and a portion 
of the chlorine, leaving the phosphates, sulphates, and a small 
amount of chlorides and carbonates. The rest, lime, 
which makes up nearly the whole, is in a caustic state. 
As the composition of these shells may be of some interest and 
value, especially to those who use them as a manure, we here 
give their analyses both before and after being burned. 
The common clam shell, (Venus mercenaria) — 100 grains of 
the unburned shell gave of 
Silica, .-.-.. 
none. 
Phosphates of iron, lime, and magne- 
sia, - 
1-250 
Carbonate of lime, - - - - 
69-204 
Sulphate of lime, (gypsum,) - 
•815 
Lime, probably combined with orga- 
nic matter, 
13-907 
Magnesia, . - - - - 
1-400 
Potash, 
1-897 
