SOILS 249

TABLE XXII.—ORGANIC MATTER BY Two METHODS

Kind of soil
Per cent loss on Ignition
after drying at
Organic matter calculated from carbon

100° 120°
; 150°

^"fcxire
9.27 7.07 5.95
9.06 6.88 5.70 5.39
! 8.50 ! 6.55 1 5.61
4.76
6.12 4.16 2.44 0.65

pas-fcure .

£ soil

subsoil ......

•T Donate Carbon. — Carbon dioxide of carbonates varies from
to 0.25 per cent in all but limestone soils. It is necessary

aow the amount of carbonate carbon in a soil before that

*rfc in organic form can be calculated.

ie method for the determination of carbonate carbon depends

i "the decomposition of the carbonate with dilute hydrochloric
£tn.d the passing of the gas into standard barium hydroxide,

excess of base being titrated with standard acid. See page
I, for details of the method.

'termination of Total Carbon. — The apparatus (Fig. 57) consists of the

ving parts: A steel cylinder, A, containing oxygen under pressure; a
e, J3, containing 30-per cent potassium hydroxide solution followed by

B

B C D F G

57.—Apparatus for the determination of carbon by combustioa.

H

Dirkaining soda lime to remove possible traces of carbon dioxide from the
5en. D, an electric tube furnace 30 cm long fitted with a combustion
j, J57, of fused quartz, vitreous silica or porcelain, 60 cm long and with an
le.cliameter of 2.5 cm, to serve for the combustion. To insure complete
.a-fcion of carbon monoxide, the last half of the portion of the combustion
3 "which is inside the furnace is filled loosely with platinized asbestos,
3hi a,cts as a catalyzer.

ortn-ection with the combustion tube is made by means of one-hole rubber
>pers and short glass tubes. The ends of the combustion tube, contain-
tlio rubber stoppers, are cooled by means of cotton wicks which dip into

*••'.

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