"We first tested your fuel in a glass cylinder to determine whether or not there was any subsidation, with the following results:

"100 cc. of the colloidal fuel with a depth of 6" was allowed to stand for 24 hours at a temperature of 115° F. At the end of the 24 hours the very top of the fuel was analyzed and that taken from the very bottom of the cylinder.

FIG. 16.-Colloidal fuel after standing one year under water.

"The top contained 33.8% insoluble in benzole.

"The bottom contained 36.4% insoluble in benzole, showing an increase of 2.6 of coal particles in the bottom over the top. This subsidation represents the particles of coal that have become destabilized since the sample was manufactured. It must not be inferred that a continuous and progressive subsidation would take place, that is, the subsidation in the second 24 hours would be only a fraction of a per cent, and would merely represent the particles

which in that time had become destabilized.

Some idea as to

the quantity can be obtained from the fact that this sample, being five months old, shows only 2.6% of the particles had become destabilized in that time.

"Three lots of the fuel 100 cc. each were then shaken up with electrolites, sodium chloride, alum and copper sulphate, 5 grams of the powdered electrolite being used to this quantity of fuel. After the three cylinders had stood 24 hours there was no perceptible difference in the top and bottom, and therefore, no apparent precipitation by the electrolites.

"We have examined your colloidal fuel thinned with benzole under the ultra-microscope and find that it is filled with particles which have the Brownian Movement. We should judge that about half of the particles visible showed this action and they varied in size from those which were quiescent to others which had had an active range of 0.00325 mm.

"We also passed the benzole solution of your fuel through the finest hardened filter paper and found that the filtrate contained numerous colloidal particles.

"We examined your colloidal fuel under the microscope and measured the size of the visible particles with 1000 diameter magnification. We noted several particles in the field .001 of an inch across and .002 of an inch in length. There were numerous particles ranging from this down to invisibility. The majority of the particles appeared to be about .0001 of an inch in diameter. There is, of course, no doubt but that the particles diminish in size to that of molecules, as was shown by an examination under the ultra-microscope, and also from the fact that we know that portions of coal are soluble in mineral oils."

Colloidal Fuel enjoys several special qualities. The calorific value per unit volume is greater than that of straight oil unless coals of very low heat value and specific gravity are incorporated. The reason is that coal is heavier than oil though of less calorific content per pound, so that the coal content most frequently raises the calorific value per unit volume. The addition of coal is not an adulteration of the oil, but it makes an increase of the heat units in the resultant gallon of liquid fuel. Thus in a composite made up of 35% by weight of pulverized anthracite coal of 14,000 B.t.u. per pound and 1.6 specific gravity and 65% oil of 18,200

B.t.u. per pound and .96 gravity, a gallon of the composite has 165,000 B.t.u., while oil has 146,000 B.t.u. per gallon.

Owing to its coal content, Colloidal Fuel is heavier, while oil is lighter than water. The character of the composite is such that it may be stored under a water seal and its fire may be quenched with water. The feature is of vast importance since an oil fire cannot be extinguished with water, and hence the rules governing the use of fuel oil are justifiably drastic. Not less than 6.4% of all fires are caused by "Fuel Oil," according to the records of the National Fire Prevention Association.

The Board of Standards and Appeals of New York City adopted a set of rules, which became effective December 1, 1919, to admit liquid fuel into the city. Rule 1 contains the following provision:

"The term oil used for fuel purposes' under these rules includes any liquid or mobile mixture, substance or compound derived from or including petroleum."

The rule is phrased so as to admit Colloidal Fuel, which is a liquid or mobile mixture including petroleum. Colloidal Fuel is also in an exceptionally favorable situation under the Tentative Regulations of the National Fire Protection Association, adopted on November 3, 1919. These set the standard in the United States and Canada. "Oil burning equipments are those using only liquids having a flash point above 150° F. closed cup tester." The word "liquids" as selected includes the new fuel. Section 1, Paragraph A, provides: "For liquids of 20° Baumé and below, tanks may be of concrete," and Section 4, Paragraph 34, states: "Where it is necessary to heat oil in storage tanks in order to handle it, the oil shall not be heated to a temperature higher than 40° F. below the flash point, closed cup." This excludes several varieties of fuel oils which require preheating over or close to their flash point in order to flow. This is not the case in the Coloidal Fuel. The Laboratory of the National Board of Fire Underwriters has certified that Grade 13, a typical example of the new fuel, had a flash point of 266° F. and Grade 15 had 273.2° F. Grades 13 and 15 were preheated in practice to about 130° F and 180° F. respectively. The apparent ignition temperature was 779° F. and 788° F. respectively, while neither gave off volatiles at room temperature or at 104° F., nor gave

evidence of spontaneous heating.

It is for these reasons that

Coloidal Fuel enjoys unusual safety features.

The combining of pulverized coal with oil and of tar with oil to make a liquid fuel has in the past had inventive devotees. As, however, petroleum does not ordinarily dissolve coal or tar, the problem was how to overcome the comparatively rapid and uncontrollable separation or settling out or sedimentation of some of the components. The present success was born immediately of the war efforts and was conceived to meet the possible shortage of liquid fuel in the Allied Navies.

The art of suspending as colloids in liquid hydrocarbons certain carbonaceous substances has been long practised. Lubricants are in use made of less than 1% of Acheson graphite of 2.1 specific gravity reduced so that the size of the particles is about 75 μ μ (within colloidal limits) and suspended in oil by the addition of gallotannic acid. Colloids of charcoal and lampblack are known. It is also reported that if coal is reduced under high pressure or high speed disk-grinding and lengthy trituration in oil, the coal may be brought into the state of stable combustible colloid.

Suspension of high percentages of particles above colloidal sizes is found to be, however, quite without precedent. So also the peptization of carbonaceous matter in liquid hydrocarbons, producing a stable composite, is new. No prior art exists for producing a stable fuel of oils having carbonaceous matter as natural impurities, like the asphaltum and free carbon found in pressure still oil. In another field, that of rendering stable a compound of two or more unmixable or partly mixable liquid hydrocarbons for fuel needs, any prior art is also of little record. Many liquid hydrocarbons will mix. Others and these of the important burning liquid hydrocarbons have till this time proved obdurate to union-for instance, fuel oil and tar have heretofore refused to mix or have mixed only partially. Emulsions have been made of non-mixing liquid hydrocarbons for use in creosoting and disinfecting, but no such emulsions much less suspensions concerning unmixing liquid hydrocarbons for use as fuels have heretofore been created.

Up to 40% by weight of pulverized coal can be suspended with 60% by weight of oil, making liquid Colloidal Fuel. Up to 75% of carbon can be incorporated in the mobile pastes. Mobile

gels can be made from either the liquids or the pastes. Colloidal Fuel may be a combination of any two or more of the forms. It will be understood, therefore, that between these states in varying blends and degrees of load, a large number of fuels either liquid or mobile, may be produced. Further, several of the forms have a natural tendency to transform themselves. For instance, liquid Colloidal Fuel stabilized for liquidity during a definite period of say, days or months, tends later to gel from the bottom of the container up. At that stage, the viscosities of the lower or gel stratum will be different from that of the thinner upper stratum. The fuel, nevertheless, has not given up the influence of its treatment. It remains atomizable, even though the gel be denser. In both layers and in the intermediate layers also, all the constituents are present and synchronize in burning. The gel thus formed is easily restored to a liquid state by heat or stirring or pumping. Sometimes even a tap upon the wall of the container will restore pristine liquid form. The colloidalizing treatment while artificially stabilizing the composite promotes also a gel formation. Conversely, the creation of a gel even in early stages helps to stabilize the compound since particles with more difficulty precipitate in a gel.

Colloidal Fuel is a composite whose particles are in three states of dispersion-solution, colloid and suspension. They give the characteristics of the three conditions. Some of the particles pass through a filter-many do not. Many are visible and measurable under microscopic inspection. Others are not. Some show active Brownian movement; others show slower movement; others no such motion at all. In considering the changes and stabilization under the treatment of Colloidal Fuel the division of the carbon surfaces must be noted. A cube of coal one centimeter on each side exposes a surface of six square centimeters. Such a cube pulverized so that 85% passes through a 200 mesh. screen exposes surfaces of about 1872 square centimeters. The ratio of surface to volume has been multiplied over 300 times. Such a cube reduced to colloidal size (or .1u diameter) develops a surface of 60 square meters-a multiplication of one hundred thousand. In Colloidal Fuel, most of the carbon particles are not reduced to colloidal sizes. Many remain much above these limits and above the colloidal borderland.

For the manufacture of the new fuel, the coal should be reduced so that about 95% passes through a 100 mesh screen and