STATE GEOLOGIST. 137 
METHOD No.71. 
As 1.685 ce. is too small a volume of marl to measure with sufficient accuracy, 
measure ten times that quantity in a hard glass tube about 95 mm. high by 15mm. in 
diameter, calibrated to contain exactly 16.85 cc. Wash into a tared tin or nickel dish, 
with the jet from wash bottle, using as little water as possible, evaporate to dryness, 
cool quickly and weigh. Jor greater accuracy take three samples from top, bottom and 
center, respectively, of the marl tank and take the average weight of the three samples. 
Grind the dried samples intimately in an agate mortar. Take two portions, each one- 
tenth the weight of the dried samples. One portion is analyzed for CaCO, by the acid- 
alkalimethod. For this purpose 4nHCL and 4nKOH solutions are the most convenient. 
The value of one cc of the HCl solution in terms of per cent. of CaCO, (or mgms. CaCO,) 
should be accurately determined by running a number of average samples of the partic- 
ular marl in use, a complete analysis having been previously made in each case by a 
standard method. This standardization of the solution with the marl to be used is very 
essential as the ease with which the acid attacks other constituents of the marl besides 
the CaCO, varies considerably in different marls. In the second portion of the dried 
sample the clay matter is determined by precipitating the silica, alumina and iron to- 
gether, with ammonia and eliminating their combined weight in the usual way. 
We now have a number of pounds of clay matter and of calcium carbonate in each 
cu. yd. of the tank marl. 
Let A = Pounds of CaCO,. 
B = Pounds of clay matter. 
C = Factor representing pounds CaCO, required to satisfy one 
pound of clay matter in the marl. 
D = Factor representing number of pounds of CaCO, required 
for each pound of clay to be used. 
X = No. lbs. clay required per cu. yd. of marl. 
Solve for X by the following formula: 
A—(BXC) 
——_———. = X 
D 
METHOD No. 2. 
To avoid the necessity of determining the clay matter in the marl, first make a num- 
ber of preliminary analyses of the particular marl bed to be worked to determine the 
combined per cent. of calcium carbonate, silica, alumina and iron in an average sample 
of marl. From samples of tank to be analyzed take as before, samples of 16.85 ce. 
each, evaporate to dryness in a tared dish, cool and weigh. One tenth the number of | 
milligrams in the dry sample equals pounds of marl per cu. yd. Take 1 gm. for analysis 
and determine by $nHCl and {nKOH solution (standardized as in method No. 1) the 
per cent. of CaCO, (or CaO as desired.) 
Let A = Pounds of marl per cu. yd. 
B = Per cent. of CaCO, in marl. 
a = Combined per cent. of clay matter and CaCO, as previousiy 
determined to be the average of marl used. 
C = Factor representing number lbs. CaCO, required for one 
lb. of clay matter in marl. 
D = Factor representing number of lbs. of CaCO, required for 
one pound clay used. 
X = Pounds of clay required per cu. yd of marl. 
Solve for X by the following formula: i 
(AXB)—CX (a—B) KA an 
D 
