CHEI\[ICAL DEPARTMENT. 147 



MARL FROM OTSEGO COUNTY. 



(Jarljonate of lime . . - 80.00 



Carbonate of magnesia 3.50 



Phosphate of lime 1. 50 



Sand and clay (insoluble in acids) Kj.OO 



^f 



Total 1 00. (HI 



Marl is sometimes found in such quantity and of such purity that it is burned 

 for lime, and alfords a fair quality of "bog lime'' for mason's use. 



TEST OF VALUE OF MARL. 



The value of marl depends almost entirely upon the amount of lime and 

 magnesia it contains, and its value is diminished in proportion to the amount 

 of clay and sand present. The lime and magnesia are found in marl mainlv 

 in the form of carbonates. A ready test for a carbonate in such cases is to 

 pour on the material some strong acid, and if a carbonate is present, it will 

 foam up or elfervesce in the same way that saleratus will foam up when vine- 

 gar is poured over it; only the effervescence wifch marl is slower, because the 

 marl is less soluble than soda. If the material does not foam when an acid is 

 added, it is not a marl, but probably a clay. 



MODE OF TESTING. 



A good way to determine the quality and value of a marl is to determine how 

 much of the material is soluble in common Muriatic Acid. This can be pro- 

 cured in any drug store, and ought not to cost more than ten cents a pound, as 

 it only costs three cents a pound. One pound of the acid Avill be enough to 

 test three or four specimens of marl. Mix the acid with one quart of rain 

 water and put this in a bottle for use. Take a tablespoouful of the material 

 supposed to be marl, put this in a large glass or earthen vessel (avoiding metal- 

 lic dishes) and slowly pour over the material a half teaspoonful of the dilute 

 muriatic acid. If it is a marl the effervescence will show this fact; if it all 

 dissolves, leaving no residue or but little at the bottom of the vessel, it is marl 

 of good quality. If but little is dissolved and a large residue is left at the bot- 

 tom of the dish, it is of iiiferior quality. 



By weighing out on delicate scales a definite quantity of the dry material, say 

 100 grains, and then weighing the washed and dried residue which is insoluble 

 in acids, an estimate can be made of the percentage of active and inactive 

 material in any specimen of marl. The insoluble residue is of no value. 



A popular and simple test to distinguish between nuirl and clay is made by 

 placing a lump of the material in a basin of water and leaving it undisturbed 

 for a short time. If it is marl it will crumble down into a diffuse mass, but if 

 clay, it will be little changed. 



USES OF MARL. 



To the farmer marl is of value mainly as a fertilizer. When found on or 

 near the farm it is the cheapest form in which lime can be applied to the soil, 

 and exerts all the beneficial influences of lime, but in a milder degree than 

 caustic lime. A certain amount of lime is required in every productive soil to 

 furnish the necessary amount of lime found in the ashes of all plants, and 

 absolutely required for their growth. But lime applied as a manure is used 



