The dealers who buy their mineral oil to mix with other kinds may even use the utmost care, and yet be sometimes deceived in the oil they buy. We can only reiterate the statement made when the first results of this examination of oil were tabulated; to wit, that the price of oil seems to have little connection with its cost, and that, if the attention of the spinner be given mainly to the quality of the oil and the character of the men of whom he buys it, his results both in respect to cost and safety will be most satisfactory to himself.

Reference has been made to the use of nitro-sulphuric acid for the purpose of testing the comparative quantity of gummy substance in the mineral oils, which is believed to be the source of stains in the cloth and of the brown varnish that is carried by evaporation and condensation to the polished parts of the machinery or deposited on the windows. For this purpose it serves well; but, as the relative portion of gum does not appear to affect the value of oil for lubrication, no further reference will be made to it at the present time.

For the test of burning oil we recommend the use of an instrument made by Pethuel Millspaugh of Kent, Conn., and sold at four dollars. It may be objected to because the cup is closed and because it is a little more severe on the oil than the open cup commonly used; but in this respect it is more like a lamp, and will be a surer guide for those who wish to buy safe oils. We have attached a second thermometer to this instrument in order to get certain results. We think no manufacturer should burn an oil that flashes in this instrument below 125° or 135° in the open cup made by Tagliabue. This standard brings in the oils known as "hundred and fifty" oils, being those which are alleged to bear a fire-test of 150°, and which, if honestly made, are safe oils.

The safety of the true 150° oils consists not only in their being less liable to the comparatively rare accident of explosion, but mainly in their not being liable to ignite if the lamp in which they are used is broken. This allegation is not made on our tests, but on the evidence of the most reliable oil manufacturers as the result of very long experience.

It has been claimed by some persons in objection to the use of the closed tester for burning oils, constructed on the plan of the Millspaugh instrument, that the flashing-point, as determined by that instrument, is 30° lower than a corresponding test with the ordinary open tester in common use.

This is an exaggeration of the facts as to burning oils. In testing twenty samples sent in at the instance of the stock underwriters, and said to have been purchased at different places in Boston, the oils which flash in the open tester at 91° to 95° F. flash in the closed

or Millspaugh tester at 83° to 88° F.; the difference not exceeding 10° on any one oil, and varying on an average from 6° to 7°.

These twenty oils did not appear to be of as low a grade as a previous lot, and most of them are evidently the ordinary "110° firetest" oils of commerce.

In order to ascertain the comparative safety of these oils, several of them, flashing at 91° to 92° in the open tester, were heated in a lamp, so arranged with a thermometer and connected with an electric battery, that a spark of electricity could be passed into the lamp above the surface of the oil at a given temperature; and, under these conditions, all these oils exploded at 80° F.

A high-flash oil (126°) exploded at 115°.

In view of these facts it certainly appears that, whatever use the public may choose to make of the oils that pass the legal inspection at 100° flash and 110° fire-test in the open cup, the managers of cotton and woollen and paper mills cannot afford to run the risk of using them.

Since this investigation was begun, a small cotton and knitting mill near Troy has been set on fire by the explosion of a kerosene lamp and destroyed. It was not insured in the mutual companies; but the writer wrote to the manager for the facts, and received answer that the package containing the oil used bore an inspection-mark of 115° fire-test. The mill was not far from the one insured by us, whose sample of oil, No. 159, also bearing an inspection-mark of 115°, flashed at 86°, and took fire at 98°, the use of which has been discontinued.

Objection has been made to the small thermometer furnished in the Millspaugh tester. In all of our trials we have used a second thermometer of the best kind, inserted through the second opening in the cover.

The common instruments for testing the anti-frictional properties of oil seem to be more fit for testing oil to be used on machinery working at slow speed and heavy pressure, or for railway service, than for spindles; but we think we can prepare instruments that will serve our purpose, and we hope to get up one that can be attached to any spinning-frame in place of a single spindle, and operated by the same mechanism. Such a testing machine seems to be mechanically possible, and, we hope, at a very moderate cost. There appears to be no apparatus now for sale adapted to the conditions of very high speed and light pressure.

A few words may here be said as to oils for oiling wool, in which the members of this association have an indirect interest as members of mutual insurance companies. Some progress has been made in

respect to determining the conditions of spontaneous combustion; but it may happen that a more important work will be done in promoting the saving and use of the natural grease of sheep's wool, now removed by alkali, and allowed to run to waste and to the pollution of rivers.

This substance is mostly saved in Europe by more or less laborious methods of recovery from the alkaline scourings. In France it is named "suint," and it is largely imported into this country under the name of" de gras," mostly for the use of curriers.

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Mrs. Richards has tried some experiments in the women's laboratory at the Institute in saving this material by leaching the wool with naphtha, and recovering the grease from the naphtha, an easy process, yielding a product almost chemically free from salts, easily saponified, and apparently possessing many valuable qualities for further use in working wool or other purposes, while the wool itself is left in very perfect condition. Of course the small experiments possible in a laboratory cannot be conclusive; but the lead is one that has greatly interested some of the most skilful woollen manufacturers and it will be followed up. The weight of grease varies from ten to nearly forty per cent of the weight of unscoured wool. One sample treated yielded twenty-three per cent fibre, thirty-eight per cent pure grease, and thirty-nine per cent dirt. The average of grease is said to be fifteen to twenty-five per cent, or at the rate of two hundred to three hundred gallons to each ten thousand pounds of raw wool, a quantity certainly worth saving, as we work about two hundred million pounds of wool a year.

The grease itself, when placed upon cotton cop waste for the purpose of testing its liability to spontaneous combustion, appeared to permeate the waste more fully and perfectly than other oils that have been tried, and proved not to have any tendency whatever to spontaneous combustion.

When mixed with three parts water and a little ammonia and borax added, it makes a white, creamy emulsion. The addition of a little pure mineral oil of high fire-test makes the emulsion a little thinner, but does not otherwise appear to alter it.

If these experiments should lead to the cleansing of wool and the saving of the "suint" by the use of naphtha, it would, of course, have to be done in separate establishments outside of the premises insured in the mutual companies; but, as it can all be done in closed vessels, the danger of the process itself would not be great. Whether this investigation will have any economic value can only be determined by actual trials on a sufficient scale. Mr. Adamson, who not long since addressed the association on the saving of cotton-seed and other waste substances, has had great experience in the use of naph

tha and benzine in his own works, and has great confidence in the economy that may be gained by its use on wool.

Mr. E. R. Flint, 106 Tremont Street, whose business it now is to clean curled hair, feathers, and woollen goods by the use of naphtha, will treat parcels of wool of from fifty pounds to five hundred pounds for experiment, at a cost not exceeding two cents per pound of raw wool, for the extraction of the grease; and a portion of grease equivalent to that belonging to the specific lot of wool will be returned with the wool. The wool will not be washed by him. It may be sent in cotton grain-bags, or in other bags, six feet long, and of the width of a common wool-bag. The wool will not be taken from the bag; and the size is important, because the naphtha is partly removed by putting the bag of wool in a hydro-extractor. The price named is merely a price fixed for purposes of experiment.

When returned to the mill the wool may be found to need only a washing in soft warm water, with a little ammonia added; and this course is recommended for experiment, in order that the dyeing of the wool that has not been treated with either acid or caustic alkali may be compared with the dyeing of wool that has been treated in the ordinary manner.

The grease on wool of the latest clip is more easily removed by the naphtha treatment than that on wool which is one or two years old.

In this connection it may be added, that leather belts are sometimes discarded because they have become so greasy as to slip, although otherwise in good condition. Mr. Flint alleges that he can treat such belts, and restore them to their original condition, except that they will be more pliable than new belts.

The undersigned does not now greatly wonder that some of his associate underwriters deemed the oil investigation rather a hopeless undertaking. It has taken, or will take, much more time than at first seemed probable and the subject has proved very complex and obscure but, whatever may be the value of this investigation for other application, it can hardly be questioned that safety from some of the dangers of fire has been promoted by it. The undersigned hopes to be sustained until the matter has been completed.

No more samples of oil will be asked, except for some special experiment; but, if any treasurer or agent desires a test, samples may be sent to the Institute of Technology, and a report will be made on the flashing and evaporation of the oil, on its liability to spontaneous combustion, on the proportion of gummy matter, and presently on its anti-frictional properties, at a charge of two dollars on each sample. It may not be amiss to state the general facts in respect to the

treatment of crude petroleum in an elementary way, as the writer, having found his own ideas of the subject far from clear when he entered upon it, may assume that possibly some of his associates may need to be enlightened by the general statement that commercial crude petroleum has a specific gravity of 45° to 47° Baumé, and is separated by distillation into three parts, - about fifteen per cent into the naphtha series, seventy-five to seventy-eight per cent into the kerosene or burning oil series, and eight to ten per cent constituting the residuum from which the lubricating oils are made.

The treatment of the heavy portion of the oil for the purpose of making lubricating oil varies greatly. All these oils are made by single or double distillation, either by fire or superheated steam, and by treatment with acids and alkali; and some lubricating oils have been sent in that are said to be made by filtration without distillation.

It appears to be the fact that there is no demand in the world for oil for lubrication to the extent of the possible supply from that part of the petroleum which would be more fit for lubrication than for burning, and that the heavy parts of the petroleum are therefore "cracked," or worked over into the more volatile products. Each section, so to speak, can thus be worked in part into the more volatile section; but no way has yet been discovered to reverse the process by converting the volatile sections into the heavier ones.

It seems to be the fact that the very lightest and the very heaviest sections have the least value in the market, and that there are ways of mixing these together so as to get any specific gravity that may be assumed to indicate a good lubricator, but that such mixtures do not stay; the volatile part evaporating, and leaving the heavy, tarry portion on the machinery. The true mineral lubricating oils depend absolutely for their quality and fitness for the work on the skill and integrity of the manufacturers.

The safest oils are evidently those which show the least evaporation, and of which apparently the least quantity is needed for the operation of the machinery. Whether there is any absolute difference in the lubricating power of these oils, when honestly made, in ratio to their specific gravity or rate of evaporation, is a question yet to be determined by our trials with frictional apparatus now just begun, on which the so-called light and heavy spindle oils will be carefully tested.

It is not believed that an absolutely stainless oil can yet be made from petroleum; but it does appear that the stains made by oil that has been skilfully distilled will bleach out without difficulty. This is a matter of inference from the fact that mills making fine cloth for