cooling, or expansion without doing evident, therefore, that something more. work, and either plan would represent a must be done than merely to re-evaporloss of useful effect. An engine con- ate the water which was condensed in structed on this system would have no the performance of work. Three courses more to do with the external atmosphere are open: We may compress the steam unthan an ordinary condensing engine has. til it occupies a space of 3.438 cubic feet, Its back pressure, however, would be or we may apply heat to it until it asjust the same as in the case of a non-con- sumes the required pressure, its volume densing engine, only in lieu of an atmos- remaining constant, or we may do both. phere of air, the exhaust steam would If the steam be compressed adiabatically, always be discharged into an atmosphere all the work expended in compressing it of steam, contained in a vessel which will be returned during expansion. would be in periodical free communica- When compressed, communication would tion with the exhaust port. The effici- be opened between the vessel containing ency of a pound of steam worked in such the compressed steam and that obtained an engine would be identical in amount by re-evaporating the water of condensawith the efficiency of a pound of steam tion. We would then at once have 1 worked in an ordinary non-condensing lb. of steam at 100 lbs. on the square inch engine, and would be considerably less to be introduced into the cylinder and do than equivalent to 150,433 foot-pounds; its work there. The cycle would thus but we could afford to disregard this loss apparently be complete, and for each of efficiency which would-as will be seen presently-be made up many fold by the novel conditions of working, provided it were possible to use the same steam over and over again.

pound of water which would otherwise have to be evaporated we would have now to convert into steam only, in round numbers, one-fifth of a pound. This represents an enormous saving.

As a matter of fact, however, the cycle is not complete. It is true that the work expended in compressing the steam may be all given back again, but it must be given back again in the cylinder, in lieu of work which would otherwise be

ized.

As regards the second scheme nothing whatever is to be hoped from it, the temperature which the steam must acquire to even triple its pressure being far too great for adoption in practice.

The cylinder of our imaginary engine has received 1 lb. of steam, but it will reject a pound of steam and water mixed, because a portion of the steam will be condensed in the performance of work. As much will be condensed as would be converted into steam of 100 lbs. pressure available for driving machinery. To from water at 212 deg. by the 206.5 put this in a practical point of view, our units of heat converted into water. As imaginary steam engine must have a 1001 units are needed to thus convert 1 large compressing pump tacked on to it, lb. of water, a very simple calculation and this pump would use up so much will show that 206.5 units will convert power that no economy would be real.206 lbs. of water nearly; consequently there will be discharged from the cylin der .206 lbs. of water, and .794 lbs. of steam at 212 deg. The water will occupy a space of, omitting small fractions, 6 cubic inches, and the steam a space of 20.93, or in round numbers 21 cubic feet. Hitherto we have regarded steam as Now, it will be seen that to restore though it was a gas, and entirely distinct this mixture to the condition of steam of from the water of condensation. 100 lbs. pressure on the square inch, practice, however, the steam would be nothing is needed apparently save to re- delivered from the engine as a cloud; it evaporate the 6 cubic inches of water, would be saturated with moisture. It is and to restore the sensible heat lost by evident that if by any device its volume the steam. But 6 cubic inches of water could be largely augmented, even withwill fill a space of 6 X 270 = 1620 cubic out increasing its pressure, by a moderinches of steam at 100 lbs. only, or 5.43 ate application of heat, that it could be cubic feet at 212 deg. This would not used over again, not, indeed, in the first, suffice to bring up the pressure to any- but in a second or condensing cylinder. thing like that which it was when steam. Now a dry gas expands by the applicawas first admitted to the cylinder. It is tion of heat at the rate of one-nth of

In

pound of air, and made to work as in an air engine. But the advantage, if any, possessed by steam over air is neutralized by the inconvenient circumstance that superheated steam exerts a solvent influence on cast iron, and cuts away cylinders and valve faces very fast.

It is not to be supposed that this is the first time that the use of steam many times over has been suggested. On the contrary, as we have shown, the economy to be effected by any scheme which would enable the idea to be carried into practice, even in an imperfect way, is so so great that many inventors have tried what they could do with the principle. The most recent effort in this direction is that of Mons. Testud de Beauregard, of the Rue Lafayette, Paris, whose invention possesses the charm of novelty

the volume per degree of temperature. under conditions different from those The value of n being 461 + t where t is which we have indicated. A pound of the sensible temperature; thus the gaseous steam may be treated like a senisible temperature of air being 212, then 461+212=673=n and expansion would take place at the rate of an increase of of the volume for each degree. But wet steam constitutes a remarkable exception to the rule; n is not a constant but a variant, and the rate of expansion is three or four times that of dry steam under certain conditions. If then heat be applied to the steam as it escapes from the first cylinder, it may be assumed that a very considerable economy may be gained. We are not aware of this plan having been fully tried. Mr. Cowper devised many years since what was known as the "Cowper's Hot Pot," namely a receiver between the high and low pressure cylinder of a compound engine, in which, by the aid of a jacket and live steam from the boiler, it was intended to raise the temperature of at all events, to a considerable degree. the steam and dry it before it entered the low-pressure cylinder. The plan was tried, but it did not succeed in effecting any saving of fuel. But it would be wrong to condemn the system as a consequence, because the failure probably resulted from the fact that the steam was not really heated or dried in the hot pot; indeed, a rise of 1 deg. or 2 deg. was the greatest attained. There is much reason to believe, nowithstanding the failure of Mr. Cowper's scheme, that if the exhaust from the high-pressure cylinder of a compound engine was led through the tubes of a superheater to do this we know from experiments of adequate size before it was admitted to the low pressure cylinder, that great economy would result; but it must not be forgotten that this arrangement would after all not provide for the use of the same steam over and over again. In other words, the steam, no matter how it was superheated or how many cylinders it traversed, must at last be thrown away; and it must be thrown away because it becomes, to use a word applied in a somewhat similar sense by Sir William Thompson, degraded. It loses both pressure and temperature, and this pressure and temperature cannot be restored by the re-evaporation of the water condensed during the performance of work. It is, however, possible to use the same steam over and over again, but

The principle on which he proposes to work is very simple. The exhaust steam from an engine is reduced to a temperature of 212 deg. by passing it through a tube coiled in a vessel of water of somewhat less temperature. This steam is then returned into a chamber or regenerator through a pipe in which is a species of induction jet of high pressure superheated steam from a small boiler. The steam pipe to the engine opens into the regenerator, and a second jet drives the steam from the regenerator into the engine. That a jet possesses sufficient power

on the use of mixed air and steam, which
we have ourselves carried out. But all
the obstacles which we have named in
the course of this article to the use of
steam twice over appear to apply to this
device. M. de Beauregard, however,
pins his faith on the result of an experi-
ment, which he thus describes:
"Wrap-
ped up in a wet cloth kept moist by
boiling water, a glass mattrass with a
long vertical neck was kept filled with
saturated steam at 100 deg. Cent. This
flask was connected to a superheating
apparatus, so as to receive therefrom,
through a special cock superheated and
desaturated steam at 500 deg. to 600
deg. Cent. On opening the cock the
flask was invariably shattered to pieces,
owing to the instantaneous expansion to

which the steam it contained was sub- cooled down from a higher temperature jected, and this happened although the to 212 deg. and saturated with moisture, large opening in the neck seemed suffici- that it is highly desirable that a very ent for the sudden expansion of the simple set of experiments should be carsteam." M. Beauregard considers that ried out, to ascertain the pressures athe has here made a new discovery: tained by condensing given weights of "The regeneration of negative steam, very highly superheated steam into the instantaneous transformation of heat given volumes of saturated steam. It into expansive power." We need hardly is not impossible that higher pressures tell our readers that M. Beauregard is could be reached than theory points out mistaken, and that he is no nearer using as probable. We have already said that steam twice over than any one else. the expansion of steam at or near the The mixture of highly superheated with boiling point is very irregular, and it is moist steam was long since proposed by apparently irregular for equal increWethered, and the system has been ments of heats. There is here a possilargely used, and with good results, but ble source of economy not yet fully exwith nothing like those anticipated by M. amined, but the broad fact remains that Beauregard. We mention his invention, steam cannot be used over and over indeed, as a warning to others. But we again through cyclical changes. At cannot help adding at the same time that least the genius has not yet come so much uncertainity exists concerning amongst us who can show how it is to the behaviour of fluids in such a condi- be done. tion of unstable equilibrium as is steam

THE PROTECTION OF WOOD AND IRON BY PARAFFINE.

From The Builder."

DR. EUGEN SCHAL gives some interest-used, especially tanks of pine wood, for ing information on this subject in the Wurtembergische Gewerbeblatt.

boiling acid and alkaline lyes, as well as casks of oak of the heaviest weights, for separating acid alizarine lyes at a pressure of a half to two atmospheres, were generally totally rotton after a few months, but they lasted for two years when impregnated with paraffine.

In chemical technology great difficulties sometimes arise when it is desired to manufacture, on a large scale, preparations which may be obtained with ease in the laboratory. In most cases the reason of this failure is the fact, that in the man- Before treating with paraffine, howufacture the use of glass, porcelain, plati- ever, the vessels must be thoroughly num, &c., which successfully resist the dried for about three weeks by leaving effects of the various chemical agents them in warm and dry air, in order to must be dispensed with, and cheaper and prepare the wood for the absorption of less easily breakable materials, such as the paraffine solution in its pores. The iron, copper, lead, and wood, substituted. latter solution is prepared in the followWood especially cannot be replaced by ing manner: A part of the paraffine is any other material in the wholesale melted in a spacious metal vessel over a preparation of muriatic lyes, although moderate fire, the mass being stirred, the the same, according to the strength and temperature of the liquid, undergoes sometimes very rapid destruction.

boiler taken from the fire, best moved into the open air, stirred until the mass begins to congeal at the edge, and then Dr. Schal says he acquired this expe- about six parts of petroleum, ether, or rience more particularly in 1874-77, in sulphuret of carbon are poured in, and alizarine manufactories, and that he stirred until solution. The preparafound in paraffine a means which effi- tion is then put into vessels that may be ciently protects the wood against damp, hermetically closed, or it may be used at acids, and alkalis, and by which a great once. In preparing the paraffine solusaving is effected. The wooden vessels tion great care must be exercised, as

paraffine, as well as petroleum, ether, or sulphuret of carbon especially, are very inflammable, and as even the vapor of the two last-mentioned substances, if mixed with air, may give rise to dangerous explosions. Those substances must, therefore, be kept in a cool space, far from light or fire, and well stoppered.

standing on their ends for half a day, after which time the remainder not absorbed was emptied, and used for the outside coating. Before applying the solution outside, however, the barrels must be well cleaned, for dirt naturally closes the pores of the wood. As these barrels were very expensive, and had to The wood is best saturated in dry and sustain a pressure of two atmospheres, warm weather, as then it dries more besides being exposed to a high temperaquickly, and a smaller quantity of the ture, they received on both sides an adsolving agent is necessary. In winter ditional coating of oil varnish. It is, six parts of the solvent generally do not however, necessary to let such a barre suffice. This proportion changes with stand in the open air at least a fortnight the quality of the paraffine and the tem- for drying, and, as a precaution, fire perature; paraffine solving with difficulty must be kept away from the barrel while is better than the more readily soluble being prepared. As a further precaution, article. Vessels easy of access, such as in applying the solution inside, the tanks, tubs, &c., are coated in the open workman must not be left alone, as it air with the solution as long as the wood frequently happens that stupefying will absorb it. The solvents evaporate vapors from the solvent of the paraffine very quickly, leaving the paraffine arise, which stupefaction, however, soon behind, so that two or three coatings disappears in the open air. The oil may be laid on in succession. If the varnish may also be diluted with petrovessel is to be exceptionally well pre- leum ether, poured into the barrel, and pared, it is left for a day to dry, and then the latter rolled about, as above then another layer of the paraffine given. described; but many places escape satuFor vessels in which steam is used for ration in this operation. After coating boiling the liquids they contain, he ap- with varnish, the barrel is once more plies after a few days a coating of oil dried, and then filled with water, in varnish, because the melting point of order to force out the combustible paraffine is below the boiling point of gases. This is much to be advised, as water, and it is thus in time driven out an explosion once took place in conseof the pores by the water.

quence of a workman trying to enlarge a hole with a red hot iron, contrary to orders. After the last operation, the inner sides of the various vessels are rubbed down with a dry duster, so as to

Instead of oil varnish, the vessels, after being well rubbed down, may also be coated with a thin solution of soluble glass, then dried and washed with diluted hydrochloric acid. The silicic take off all loose particles. acid thus formed clogs up the pores If impregnation of wood is intended. from the outside, and provides a protec- on a large scale, the wood is best stacked tion to the paraffine against the hot in iron boxes, the paraffine solution. water. For vessels which are used only poured over it, the solution not absorbed with a moderate heat or cold, the coat-drawn off after some time, the solvent ing of paraffine suffices perfectly. The forced out of the wood by means of paraffine is hardly dissolved by diluted warm air, and recovered by condensation cold alcohol, is not poisonous, and may in a cooling apparatus. also probably be used with advantage| If the various manipulations are carefor vessels for keeping liquid. In the case of barrels, the solution was poured in simply after drying them; for an oak barrel holding nine to ten hectoliters, 1 kilo of paraffine dissolved in petroleum ether was required. All openings were then well closed and the barrel rolled about and over for about an hour, so as to bring all parts in contact with the solution. The barrels were finally left

fully carried out, the duration of vessels thus prepared is increased from four to six fold, while the outlay is comparatively small, leaving out of consideration that the contents of such vessels are frequently lost by the bottom being forced out.

Paraffine, melted with equal parts of linseed oil or rapeseed oil, is also useful for coating iron vessels, which, without a

substantial preservative, are very liable to rust in manufactories of chemicals. Paraffine likewise protects skin efficiently against wet, alkalis (especially lime), acids, &c.

Dr. Schal says he often found that workmen in alizarine factories suffered much from sore, ulcerating and swollen hands, especially during winter. After the workmen began to use (twice daily) a solution of paraffine with rapeseed oil and petroleum, chapped hands. became a scarcity.

The solution is produced by melting three parts each of paraffine and rapeseed oil, removing it from the fire, and adding eight parts of petroleum while stirring the mixture. Before using, the solution is stirred a little, and the hands rubbed with it while they are clean and dry. In larger factories, earthenware and tin vessels, filled with this ointment, are placed at convenient spots, and it is believed that the manufacturer, as well as the workman, will find this pay.

ON THE STRENGTH OF IRON AT HIGH TEMPERATURES.

By J. KOLLMANN.

From "Abstracts" of the Institution of Civil Engineers.

inch). They were brought up to the required temperature by heating either in a coke fire or a portable forge; two exactly similar pieces being used, one for the experiment and the other for the determination of the temperature, which was done by means of a water calorimeter of a somewhat special construction. The final temperature of the broken test piece was sometimes determined in the same way, but generally the loss of heat was computed by observing the time and applying the results of a table specially computed from masses of iron allowed to cool in the air for definite periods.

In this memoir the author gives the results of a series of investigations carried out in 1877-78 at the Oberhausen works upon the tension and resistance to compression of wrought iron and steel at high temperatures, which, together with other experiments, were undertaken to obtain a basis for a theory of the action of the rolling mill and of the construction of rolls. The materials investigated were of three kinds, namely, fibrous malleable iron, fine-grained iron, and mild Bessemer steel, the samples used being of the average ordinary qualities produced in the works. Two testing machines were used: in one the strain was The experiments were made at temapplied by hydraulic pressure, and in the peratures varying from 20° to 1,080° other by weights applied directly. The Centigrade, and the progressive diminuelastic limit was determined by a con- tion in strength is expressed in terms of trivance called a multiplier, consisting that at 0°, the latter being made = 100: of a pair of unequal armed levers with set screws on the shorter arms, whereby they are attached to the test piece. Centigrade. These remain closed while there is no permanent elongation, but when the limit of elasticity is reached the arms separate, the divergence being read off on a divided scale attached to the longer sides.

Fibrous
Iron.

Fine-
Grained

Bessemer

Iron.

Iron.

0

100

100

100

100

100

100

100

200

The experiments were made with test pieces of two different sizes; those for the smaller hydraulic machine were either round, of 13 millimeters (0.51 inch) diameter, or square of the same dimensions on the side. Those for the larger one meas-(Verhandlungen des Vereins zur ured 40×10 millimeters (1.575 X 0.394 Beforderung des Gewerbfleisses.)