16 
BULLETIN 6 2, HAWAII EXPERIMENT STATION 
Table 4 shows the true and apparent specific gravities of 21 
Hawaii soils as determined by the procedure described above, and 
the porosity of these soils as calculated from the two specific 
gravities. 
Table 4. — Specific gravity and porosity of Hawaii soils 
Soil No. 
True 
specific 
gravity 
Appar- 
ent 
specific 
gravity 
Porosity 
Soil No. 
True 
specific 
gravity 
Appar- 
ent 
specific 
gravity 
Porosity 
2 
2.83 
2.98 
2.19 
2.53 
2.31 
2.79 
2.57 
2.52 
2.79 
2.68 
2.52 
2.84 
1.25 
1.32 
.66 
.93 
.98 
1.19 
1.04 
1.04 
1.16 
.93 
.96 
1.04 
Per cent 
55.8 
55.7 
69.9 
63.2 
57.6 
57.3 
59.5 
58.7 
58.4 
65.3 
61.9 
63.4 
48 
3.36 
2.70 
3.24 
3.31 
2.86 
2.98 
2.90 
2.92 
2.96 
1.32 
1.06 
1.32 
1.25 
1.04 
.94 
1.17 
1.09 
1.14 
Per cent 
60.7 
6 
49 
60.7 
9 
56 
59.3 
12... 
57... 
68.3 
15... 
65... 
63.6 
17... 
66... 
68.5 
21... 
69... 
59.7 
23 
76 
62.7 
31 
77 
61.5 
33 
Average 
37 
2.80 
1.09 
61.5 
42 
As was anticipated, large variations were obtained. Soils with 
larger percentages of organic matter gave on the whole much lower 
figures than soils of low organic content. The lowest figure recorded 
was 2.19 for soil No. 9 — a highly organic, light-gray soil containing 
18.5 per cent organic matter ; whereas the highest figure recorded was 
3.36 for soil No. 48 — a brownish-red, ferruginous clay of 6.67 per cent 
organic content. The average for all the soils was 2.8 despite the fact 
that the series contained several abnormally organic soils which 
lowered the average. In the case of soils the organic content of which 
was below 10 per cent, the specific gravity averaged 2.96, whereas for 
soils the organic content of which was over 10 per cent the specific 
gravity averaged 2.47. 
In determining the volume weight or apparent specific gravity, it 
is realized that the figures are only approximate and that they do not 
represent actual field conditions in so far as structural 1 relationships 
are concerned. The high percentage of organic matter in Hawaii 
soils is one of the main determining factors and is often the cause of 
considerable variation. On the whole, the apparent specific gravity 
of Hawaii soils is much lower than that of the mainland soils 
partly for the above-mentioned reason and partly on account of the 
finer texture. For the whole series it averaged 1.1, the values fluctuat- 
ing between 0.66 in soil No. 9, a highly organic kind, to 1.32 in soil 
No. 6, an inorganic clay resembling adobe. 
The percentage of pore space calculated from the specific gravities 
indicates the fine texture of the Hawaii soils. As is known, coarse 
soils are much heavier than fine soils, because of the nature of the 
contact of the particles and their disparity in resisting compaction. 
The method employed in determining the apparent specific gravity, 
when disturbed soil is used, gives lower results for that constant than 
does either the iron-cylinder or the paraffin-immersion method. On 
mainland soils the apparent specific gravity determined by the iron- 
cylinder and the paraffin-immersion methods gave results 0.4 higher 
