1

peared; Henry Bird, of Newark, N.J., made a mixture in which he used a little kerosene oil with strong soap-suds. He said that "it readily combines and can be applied uniformly with a syringe."

Although it is not definitely stated in the two cases just mentioned that emulsions were secured, still there can scarcely be any doubt that at least a part of the oil was emulsified. Who, then, is the originator of the, or a, kerosene emulsion? The answer is undoubtedly to be found in the unrecorded work of some unknown but intelligent grower of plants.

Cook was probably the first experimenter to recommend the use of a mixture of kerosene oil and soap water. He says: "I found it [kerosene] would mix permanently with soap solution in 1877 and 1878, and that it would kill many insects if it touched them, and best of all would destroy haustellate insects like bugs, plant and scale lice. I first recommended this to the public in 1878.3 ... The best substances for such use (killing haustellate [sucking] insects) are a weak solution of carbolic acid, a strong suds either of whale-oil or common soap, and tobacco water. I have found that the addition of a half teacupful of crude petroleum to two gallons of either of the above makes them the more effective. .. I mix one quart soft soap, or one-quarter of a pound of hard soap, with one or two quarts boiling water; as soon as the soap is all dissolved, I stir in, while all is yet hot, one pint of kerosene oil. This is now violently stirred till it is permanently mixed — that is, till upon standing the oil will not rise to the top, but will remain incorporated with the liquid. . . . When we are ready to use this, stir in enough water to make fifteen pints in all that is, one-fifteenth of the liquid applied would be kerosene oil." These formulas, using either the hard or the soft soap, have received the name of the originator, and they are still in common

use.

Riley published the following in the annual report of the Commissioner of Agriculture for the years 1881-82, 127: "Emulsions with soap-suds and lye had been worked at some

1 "T. A." in Gardener's Monthly, 1868, June, 106. See, also, Country Gentleman, 1876, July 6, 422, citing from The Agriculturist.

2 Mich. Agric. Exp. Sta. 1890, March, Bull. 58, 5.

3 See Rept. Mich. State Board of Agric. 1878, 434.

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years ago by Professor Taylor, the microscopist of the Department, and more recently they have been made by several independent experimenters in Florida, but particularly by Mr. Joseph Voyle,1 an intelligent correspondent at Gainsville, who uses kerosene, soap, and fir-balsam combined at a high temperature and produces a permanent paste which he calls ‘murvite,' readily soluble in water. Recent experiments made at our request by Mr. Clifford Richardson, assistant chemist of the Department, with ordinary soap, whale-oil soap, and both light and heavy oils, also show that 20 parts hard soap, 10 parts water, 40 parts kerosene, and 1 part balsam, produce the most satisfactory results. Mr. Hubbard's experiments would indicate, however, that for insecticide purposes nothing equals the milk emulsions which were first suggested by Professor Barnard 2 during our work on the cotton worm at Selma, Ala., in 1880, and though the use of ordinary emulsifying agents, as various mucilaginous substances and the phosphates, lactophosphates, and hypophosphates of lime, may facilitate the making of kerosene emulsions, we have not yet had them sufficiently tested as insecticides, and for the present can recommend nothing more simple and at the same time more available to the average farmer than the permanent milk emulsion as produced by Mr. Hubbard."

During the season 1881-82, Mr. Hubbard was making experiments for the destruction of the scale insects affecting orange trees. He made the milk emulsion only, and of varying strengths. The following is the formula recommended at the close of the season's work: "Refined kerosene, 2 parts; fresh, or preferably sour, cow's milk, 1 part (percentage of oil 663). Where cow's milk is not easily obtained, . . . it may be replaced by an equivalent of condensed milk (Eagle brand) diluted with water in the proportion 1 to 2. . . . In applications for scale insects, the kerosene butter should be diluted with water from 12-16 times."

Under date of Sept. 15, 1881, Mr. Hubbard writes to Dr. Riley regarding the condition of the work on orange scale then

1 See U. S. Dept. of Agric. Div. of Ent. Bull. 1, 19.

2 For further details concerning W. S. Barnard's suggestion of an emulsion of milk and kerosene, see The Official Gazette U. S. Patent Office, Vol. 59, No. 12, 1919. 3 Ann. Rept. U. S. Com. of Agric. 1881-82, 113, 114.

in progress at Crescent City, Fla.1

"Experiments with

Neal's mixture gave, upon the whole, rather disappointing results." I have not learned what was the composition of this mixture, but it may have been an emulsion of kerosene in soap water, for Dr. Neal did considerable work in this direction. On Oct. 10, 1882, he wrote from Archer, Fla., to the chief of the Division of Entomology regarding these formulas, only two of which it is necessary to mention. These were also applied for the destruction of the cotton worm:

"1. Four pounds whale-oil soap were dissolved in one gallon of water with heat; to this, kerosene was added gradually till it was found that one gallon kerosene made a good emulsion, capable of being diluted to one per cent without at once disintegrating.

"2. Four pounds resin soap, common bar or yellow soap, were dissolved in one gallon water. One gallon kerosene gradually added, with constant agitation. The greater the per cent of resin in the soap, the better was the emulsion I found it made, which would indicate that such a soap for this purpose would no doubt be a valuable article in the market."

On Nov. 28, 1882, Hubbard wrote in detail concerning the use of kerosene, and also criticised Neal's formulas. He says: 3

"Experiments made in September with kerosene washes on purple scale show that the eggs are much more difficult to kill than I had supposed. They have been killed by 66 per cent kerosene and soap emulsions diluted 1 to 9. . . I have carefully gone over Dr. Neal's report and have a few comments to add to my former communication.

"Dr. Neal says 'the greater the percentage of resin in the soap the better the emulsion I found it made.' This may be true of the emulsion, but when diluted, the resin, or a large part of it, separates from the liquid and forms a waxy scum on the surface, which clogs the pump and nozzle, and is troublesome unless removed. . . . The strongest emulsion used by Dr. Neal contains 50 per cent of oil and the strongest wash a dilution of 1 to 9. My experiments with milk emulsion of this strength did not in the end prove satisfactory, and I long ago decided to

1 U. S. Dept. of Agric. Div. of Ent. 1883, Bull. 1, 10.
2 Ibid. 32.

3 Ibid. 17, 18.

increase the amount of oil in the emulsion. I now use 66 per cent emulsion diluted 1 to 9, and these, although sufficiently strong for long scale, are not sufficiently penetrating to kill the eggs of purple scale. The following are my estimates for a standard wash of whale-oil soap and kerosene, emulsion 66 per cent oil, diluted to 1 to 9 (one gallon emulsion=10 gallons wash): whale-oil soap, pound; water, 1 gallon; kerosene, 2 gallons.”

...

In the annual report of the Commissioner of Agriculture for 1884 a formula is published which contains twice as much soap as Hubbard's original one, the other ingredients remaining the same. This has become most commonly known under the name of the Riley-Hubbard formula for the kerosene emulsion, and is used to-day unchanged. It is prepared as follows:

66 Kerosene, 2 gallons; common soap, pound; water, 1 gallon. "Heat the mixture of soap and water and add it boiling hot to the kerosene. Churn the mixture by means of a force pump and spray nozzle for five to ten minutes. The emulsion, if perfect, forms a cream, which thickens on cooling, and adheres without oiliness to the surface of the glass. Dilute with cold water before using, to the extent which experience will indicate is best."

The scale insects found upon the orange trees in California may be cited as further examples showing that obstacles can be overcome if only sufficient attention is directed towards them. These insects were a serious pest on the Pacific coast, and they are not entirely under control even at the present day, but their great numbers in former years aroused the fruit growers to energetic measures. Many compounds were recommended for the treatment of the pests. The preparations were generally in liquid form, and may be considered as rather elaborate outgrowths of compounds whose value had long been known. The following are good examples of these remedies, whose number was almost endless: 1

1. Forty-six pounds whale-oil soap, 4 gallons coal oil, 100 gallons water.

2. Twenty-five pounds brown soap, 6 pounds wood potash, 4 gallons coal oil, 100 gallons water.

1 Ellwood Cooper, "California Fruit Culture," a report of the fifth annual convention of California fruit growers.

3. Ten pounds whale-oil or other soft soap, 2 or 3 pounds sulphur, 1 gallon coal oil, 17 gallons water.

It will be seen that soap or kerosene, or both, formed the basis of most of these washes. They were not entirely satisfactory, for some reason still unexplained. In 1886, D. W. Coquillett and Albert Koebele, were appointed by the Department of Agriculture to investigate the trouble, for in the East such emulsions were used almost invariably with good results. In a review of their work, published in 1887, Dr. Riley makes the following statements, which indicate well the character of these investigations: 1

Among the different substances thoroughly experimented with were caustic potash, caustic soda, hard and soft soaps, tobacco soap, whale-oil soap, vinegar, Paris green, resin soaps, and compounds, and so on. . . . Mr. Koebele's attention was, however, directed mainly to the preparation of resinous soaps and compounds on account of their greater cheapness. He succeeded in making a number of these mixtures, which, when properly diluted, need not cost more than one-half to one cent per gallon, and which produce very satisfactory results, killing the insects or either penetrating or hardening the egg masses so as to prevent the hatching of the young. One of the most satisfactory methods of making a resin soap is to dissolve 1 pound of caustic soda in 1 gallons water to produce the lye ; then dissolve 2 pounds resin and 1 pound tallow by moderate heat, stirring in gradually during the cooking 1 quart of the lye, and then adding water until you have about 22 pints of a brown and thick soap. This will make 44 gallons of wash, costing less then one-half cent per gallon."

A few further suggestions were made regarding various combinations of the above mixture, and the addition of adhesive substances to the washes was strongly advised. But the most important part of this address was the emphasis laid upon the value of the resin washes, for from this time on they were destined to extensive use in the orange district of California.

1 Address by Professor C. V. Riley before the California State Board of Horticulture, at its semi-annual session at Riverside, Cal., April 12, 1887, as reported in the Pacific Rural Press, April 23, 1887, cited in Bull. 15 U. S. Dept. of Agric. Div. of Ent. 16, 17. See also Ann. Rept. U. S. Com. of Agric. 1886, 558, giving details of Koebele's work.