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to the arsenic solution; and even then only a faint amber discoloration may appear, because of
the small amount of sulfur in the water. The mineral water test, therefore, is practically out of the question.
This test of arsenic determines only the fact that soluble arsenic is or is not present. It does not determine how much soluble arsenic there may be; although the greater or less amount of the yellow color on precipitation will afford a comparative idea of the amount present in any two or more samples.
It has already been advised to use lime with Paris green or London purple for the purpose of taking up the soluble arsenic, by the formation of arsenite of lime. If this is done, or if the Bordeaux mixture is used with the arsenites, it will not matter if the poison contains soluble arsenic.
11. How can one determine if Paris green is pure?-It sometimes happens that material which is obtained as Paris green contains no arsenic. Chrome green may be sold instead. If the material is pure Paris green, it will quickly and completely dissolve in common strong ammonia, giving a beautiful, rich, dark blue, clear liquid, whilst any of the compounds which would ordinarily be substituted for Paris green on account of their color and texture, will not behave in this manner in ammonia. Any insoluble residue is impurity. Chrome green will not dissolve in ammonia.
12. What becomes of the arsenic when it falls upon
Arsenic in the Soil.
the soil?-With the action of the rains and the falling of the leaves, most of the arsenic which is applied to trees finally reaches the soil. What then becomes of it? If lime has been used with the spray, the arsenic will be insoluble when it falls upon the soil. It is possible that the organic acids in the soil, and also carbonic acid, may dissolve some of the arsenic, but it would be almost surely made immediately insoluble again by combination with lime or other soil constituents. If soluble arsenic is placed on the soil, it probably almost immediately goes into insoluble combinations, and remains where it was placed unless slightly washed down by mere mechanical means. Now, some plants appear to have the power to take up very minute quantities of arsenic and still thrive-probably so minute that the nicest chemical test can scarcely discover it,-but any appreciable quantity of soluble arsenic in the soil quickly destroys the roots. If, therefore, the grass and other plants under sprayed trees continue to live, there need be no fear that the arsenic will injure the soil.
A study of the destination of arsenic which has been applied to the soil in the form of Paris green was made at the Cornell Station (Bulletin 101), from which the following conclusions were drawn : "The gist of the whole matter then, if we may generalize from these tests, is that the arsenites do not leach from the soil. They remain where they fall, the same as sand does, and are carried down only when there are crevices or other openings in the soil, and they then go down as insoluble compounds, and to
a slight extent, by the mere mechanical action of the water. It is really remarkable that sand was such a perfect filter as to hold the great quantity of arsenic above a depth of three inches for over four months. If the soil in either experiment had been a homogenous subsoil, where the sun could not have cracked or checked it, it is fair to conclude that no arsenic could have penetrated it."*
Summary.-The fruit-grower may desire to have a very brief epitome of some of the cardinal suggestions touching spraying:
1. Spraying is only one of several means or operations which the pomologist must master if he aspires to the greatest and most uniform success. Other fundamentally important requisites are tilling, fertilizing and pruning.
2. Spraying is not necessary to successful results every year, but inasmuch as the farmer cannot foretell the need of the operation, he should spray as a matter of insurance.
3. Spraying is almost sure to be of some benefit every year, particularly upon apple, pear, plum and quince trees, and upon grape vines.
4. Spraying is of little consequence unless carefully and honestly done. The spray must actually reach every point which it is intended to protect.
5. Prepare for the year's campaign during the previous winter, by reading the last teachings, and
*For another discussion of this subject, and of the destination of copper in the soil, see Lodeman, "The Spraying of Plants," 231-237.
by completing pumps and appliances. Give particular attention to a convenient wagon outfit.
6. The Bordeaux mixture need not be made up at each using in the exact numbers of the formula. The copper sulfate may be permanently dissolved in water and the lime may be slaked. When the mixture is prepared, the stock solution of vitriol is diluted, the lime added, and the tank filled to the required amount.
7. Spraying is of small account unless the operator understands precisely what he sprays for.
8. The time to spray is when the operation is needed to protect the plant. This will vary, therefore, with every season and every different pest. In general, apples and pears need spraying twice, first when the fruit-buds open, but before the flowers expand, and again when the blossoms fall.
9. The presence of soluble arsenic in Paris green may be determined by a test with sulfuret of hydrogen.
10. Pure Paris green dissolves in ammonia, giving a rich, deep blue liquid.
HARVESTING AND MARKETING FRUIT.
ALTHOUGH the management of the business or commercial side of fruit-growing-the importance of which is urged in the first chapter-is very largely a matter of personal temperament, nevertheless a few general remarks by way of suggestion may be given to the subject. The business part of fruitgrowing is chiefly concerned with the broad subject of marketing the fruit, which may be considered under the four heads of picking, packing, storing and shipping. The actual selling of the product is an enterprise which belongs rather to the merchantman than to the fruit-grower.
When to pick.-Just when and how the fruit should be picked for best market results depends very largely upon the species or variety of fruit, and greatly, also, upon the distance to which it is to be shipped. The closer and better the market, the riper the fruit should be when it is taken from the plant. If one is fortunate enough to have a special or personal market, delivering the fruit to