TABLE No. II.—SHOWING THE HYGROSCOPIC WATER CONTAINED
BY STARCH PRODUCED FROM DIFFERENT PLANTS.
Percentage
of water.		Remarks.
1. Potato20.27Commercial, locality unknown
2. Sweet potato19.57C., C.L.**
3. Buck yam19.43C., C.L.
4. Barbados yam19.40C., C.L.
5. Arrowroot18.81Bermuda, commercial
6. Irish potato17.28Tubers from Belfast, C.L.
7. Guinea yam17.14C., C.L.
8. Tous les mois16.74Grenada, commercial
9. Arrowroot16.43Barbados, ditto
10. Common yam16.36C., C.L.
11. Plantain16.23C., C.L.
12. Arrowroot15.65C., C.L.
13. Arrowroot14.84C., Plantation Enmore
14. Tous les mois14.64C., C.L.
15. Tannia14.60C., C.L.
16. Sweet cassava14.30C., C.L.
17. Maize14.22C., C.L.
18. Arrowroot13.36C., C.L.
19. Bitter cassava11.88C., C.L.
20. Wheat starch11.16Commercial, of English manufacture
[** The initial C. throughout these tables indicates that
the plant was grown in the colony; C.L., that the starch
was prepared in the colonial laboratory.]

That the extremes in this table should occur in the case of the starches of commerce, was, perhaps, to be expected; nevertheless the difference between the starch of the sweet potato and that of the bitter cassava is nearly as great, and both these specimens were prepared in the laboratory, by the same process, and subject to the same temperature and exposure.

Characters of the jellies formed by various starches.—Tenacity.—I have met with no very precise results on this subject, except the well-known fact that it takes a much larger quantity of some starches, the arrowroot for instance, to form a jelly of equal tenacity with that formed by others, such as the Tous les mois; and hence in the West Indies the latter is universally preferred to the cassava starches.

After trying various plans, the method which I found best fitted for comparing the tenacity of different starch jellies, was the following:—Of each of the kinds of starch, 24 grains were weighed out and mixed with 400 grains of distilled water, in a porcelain capsule of suitable size. The mixture was then heated and boiled briskly for three minutes, with constant stirring, and was immediately poured into a conical test-glass,[45] which the jelly nearly filled. The time at which each glass was filled was noted, and exactly two hours were allowed for the contents to cool in a current of air. The glass is then set on a plate of glass, supported on a ring of a retort stand, and the weight ascertained, which was necessary to force a metallic disc, of ascertained size, through the jelly. The most convenient way of doing this was by using a piece of apparatus of the form rudely represented on the margin. The rectangular frame is of thin brass wire, and the slightly cup-shaped disc, d d, is soldered to a wire, attached to the upper short side of the rectangle. From the opposite or lower side of the rectangle a small glass cup, c., is suspended, into which weights are put as soon as the disc has been made to rest on the surface of the jelly, pp is the plate of glass on which the test-glass is set. Whenever the disc tears the skin of the jelly and begins to sink in it, no further addition, of weights is made, and the weight of the disc, framework, and cup being known, we have an estimate of the tenacity of the jelly. This process is but approximative, and some practice is necessary before the operator succeeds in getting uniform results from the same series of specimens.

The following statement shows the results on such specimens as I could procure. The disc was exactly 7/10ths of an inch in diameter.

TABLE NO. III.—TENACITY OF STARCH IN JELLIES.
No.Names of specimens.Weight in grains required
to break the jelly.
1.Tous les mois, C., C.L.2,446 *
2.Tous les mois, Grenada, Commercial1,742
3.Maize, C., C.L.955
4.Barbados yam, C., C.L.895
5.Irish potato, from Belfast, C.L.756
6.Tannia, C., C.L.630
7.Bermuda arrowroot, finest Commercial627
8.Common yam, C., C.L.657
9.Guinea yam, C., C.L.571
10.Plantain, C., C.L.467
11.Potato starch, Commercial467
12.Arrowroot, C., C.L.393
13.Sweet potato, C., C.L.368
14.Arrowroot, C., C.L.340
15.Arrowroot, C.301
16.Arrowroot, St. Vincent's, Commercial289
17.Barbados arrowroot, Commercial273
18.Wheat starch, Commercial183
19.Buck yam, C., C.L.151
20.Bitter cassava, C., C.L.150
21.Sweet cassava, C., C.L.78
[* In this instance the weight stated detached the jelly from the sideof the glass,
but the skin of the jelly was not torn as in the other cases.]

From this list it is obvious that, in respect of tenacity, there is a very great difference between the jellies prepared from the different starches—greater, indeed, than exists in regard to any other character. At first I thought it probable that the tenacity of the jelly would bear some relation to the size of the globules, and it is true that we find the Grenada Tous les mois, the largest globule, next the top, and the cassava among the smallest, at the bottom of the scale. But, on the other hand, we have the Buck yam starch, a large sized globule, very high; together with many other exceptions.

As an article of diet, the most tenacious varieties of starch are preferred, on account of the economy of employing an article of which a less quantity will suffice; and the same is true when applied to starching linen, provided the jelly be not deficient in clearness.

Clearness of jellies.—When starch jelly is used for the purpose of starching, or glazing linen, or cotton goods, those varieties that are most transparent are understood to be preferred, provided, at the same time, they possess the requisite tenacity. This and other matters will be best determined by practical men in England; but having had occasion many times to prepare specimens for trying the tenacity, the opportunity was always taken of arranging the specimen of jellies in the order of their clearness, or, to speak more accurately, of their translucency. In this respect also they exhibit considerable differences, varying, when prepared according to the formula described under the head of tenacity, from very translucent approaching to opaque. The order is shown in the annexed list, which begins with the clearest.