Table 5.

Table 5. Neutralization potential (NP) values (metric tons per 1000 metric tons) for four digestion methods and two titration techniques of 31 overburden samples. The samples were separated into four groups based on mineralogy and elemental composition.

Samples	Sobek Hand	BOIL Hand	Sobek Auto	H₂O₂ Hand	H₂O₂ Auto	SobPer Hand	Difference High - Low
Fe
1	70 a¹	89 a	11 b	16 b	7 b	14 b	63
2	62 a	88 a	15 b	19 b	9 b	21 b	79
3	63 a	87 a	11 b	17 b	10 b	15 b	77
4	62 a	95 a	8 b	15 b	12 b	5 b	87
5	64 c	82 c	288 a	56 c	139 b	25 c	263
6	367 a	356 a	324 a	322 a	245 b	250 b	122
Ca
1	926	936	926	924	928	926	12
2	835	843	834	847	841	840	13
3	711	724	710	728	708	711	18
S
1	-23 b	-26 b	-38 b	-74 ab	-35 b	-113 a	90
2	78 a	76 a	75 a	31 b	75 a	-7 c	85
3	79 a	79 a	17 b	33 b	16 b	-----	63
4	-1 b	-1 b	1 b	-16 a	-1 b	-33 a	34
5	23	23	14	18	12	-----	11
Si
1	5	5	5	4	6	3	3
2	2	2	4	1	6	-3	9
3	2	1	3	1	3	-2	5
4	15	16	18	16	19	14	5
5	64	59	75	64	77	63	18
6	-1	-2	3	-4	5	-7	13
7	-5 b	-5 b	-1 a	-6 b	1 a	-11 b	12
8	-7 ab	-7 ab	-4 a	-9 b	-1 a	-14 b	13
9	-2 a	-11 a	-1 a	-25 b	-1 a	-25 b	24
10	18	13	13	12	------	7	11
11	40 b	73 a	13 c	20 c	15 c	12 c	61
12	23	19	11	15	14	8	15
13	113	109	114	112	131	110	22
14	7	7	13	9	15	6	9
15	23 b	40 a	25 b	24 b	25 b	4 c	36
16	17 b	62 a	11 b	23 b	12 b	10 b	52
17	88 a	88 a	20 b	26 b	19 b	-----	69

¹ Values within rows without letters are not significantly different; within rows with different letters are significantly different at p < 0.05.

Effect of Digestion Method, Siderite Content, and Fizz Rating on Neutralization Potential of Overburden Samples