ON THE PRODUCTION OF FRESH WATER FROM SEA WATER.

Colonist, Issue 99, 1 October 1858, Page 3

ON THE PRODUCTION OF FRESH WATER FROM SEA WATER.

BY BR. A. NORMANDY. "

(From the New Zealand GazMe.)

Sea water is, as everybody knows, a liquid, which contains from three-and-a-half to four per cent, of-Saline substances, two thirds of which are comiiion salt, and also a certain portion of organic matters, which impart to it its well-known odour and taste, and render it unfit for drinking or other domestic purposes. The accidents resulting ffcom an insufficient supply, or from an absolute want of fresh water 'iv sea voyages, the difficulty of preserving in a pure state that which is stored up, or of procuring a fresh supply of it when it is exhausted, the valuable stowing room occupied by the tanks containing this most important fluid, have induced many people at various times, and for a gre vat many years past, to contrive apparatuses by means of which sea water could be rendered fit to drink.

m At first sight, one would think that it is sufficient to submit sea water to distillation to convert it into fresh water, and that the solution of the problem is altogether dependant upon a still, constructed so as to produce, by evaporation, a great quantity of distilled water, with a consumption of fuel sufficiently small to become practicable.

Distillation at a cheap rate is, doubtless, an important item, and fuel being a cumbrous and expensive' article on board ship, it is superabundantly;;|vident that, supposing all the apparatuses wnich have hitherto been contrived for the purpose to answer equally well, that one would clearly merit the preference which would produce most at the least cost; but there are besides other desiderata of a no less primary importance, and it is from having neglected, ignored, or been unable to realise them, that all the apparatuses for transforming sea water into fresh water, which have from time to time been brought before the public, have hitherto, without exception, proved total • failures, or (after trial) have been quite discarded, or fulfil the object in view iv a way so imperfect or precarious, that, practically speaking, the manufacture of fresh water at sea may be said to have been until now an unaccomplished feat. The other desiderata above alluded to are these:—

When water, whether salt or fresh, is submitted to distillation, the condensed steam, instead of yielding, as might be supposed, a pure, tasteless, and odourless liquid, has always an almost intolerably nauseous, empyreumatic taste and odour, which it retains for many weeks. This taste and odour, which are so disagreeable, and the water so produced being, as is the case with ordinary distilled water, deprived of air by boiling, is on that account, so heavy, so indigestible, and vapid, that the crews invariably refuse it as long as they can obtain a supply, from natural sources, even though this may be of so bad a quality as to endanger their health or their lives, as evidenced by the report of the Times own correspondent,- in reference to the water; supplied to the crews of our ships in the Baltic during the late war.

With a view to remedy these defects, chemical re-agents, such as alum, sulphuric acid, muriatic acid, chlorine, chloride of lime, &c, to be added to the distilled water, have been proposed; but it is evident that the continuous and daily absorption of chemical re-agents might, and doubtless would, cause accidents of a more or less serious nature, not to speak of the trouble and care required in making such additions, an excess-of :j which might be attended with dangerous, and possibly with fatal consequences; besides, as a general rule, we have the authority of Liebirf to say, that the use of chemicals bi.o!ild never be recommended for culinary purposes, To. .chemicals are seldom met with in commerce inV&t*i-nf purityj andare freque ntly contaminated by poisoho^ substances. On the other hand, the pumps, Ventilators, bellows, agitators, the percolation throttj-i., porous siibstances, through plaster, chalk, sancir&c.rwh.ok have been proposed to aerate .the water obtained, and render it palatable, are of a difficult, inconvenient/ or impossible application ; they are costly, complicated, bulky, or unmanageable; and as to leaving the distilled water to become aerated by the agitation imparted to it in the tanks by the motion of the ships, the report of the correspondent of the Times, above alluded to, shews that this method is attended with but 'indifferent success. I shall presently explain why no system or method of aeration whatever could be attended with success except under certain conditions, and unless it be done in a certain manner, conditions and manners realised in my apparatus.

Another desideratum lost sight of in the endeavors which have been made to accomplish the object, (and it is a condition of extreme importance) is to obviate, or prevent the deposit of saline matter which takes place in the apparatus when the limit of saturation has been attained, and which, in a short time after use, interferes temporarily at least, often permanently, with the working of the apparatus, renders frequent repairs necessary, and in all cases eventually destroys it.

The expansion of metals by heat and their contraction by cold, is another source of failure; so much so, that it can be most truly asserted, without fear of contradiction, that any fresh water distilling apparatus for marine purposes, in any part of which solder is employed, is ipso facto, defective, and ought not to be trusted, the soldered parts being sure to give way from the cause just alluded to, and this perhaps (as tlie event has unfortunately more^ than once proved) at a. time when tbe machine was most wanted, its unsoundness thus creating the most distressing sufferings, and putting the fives of all on board in imminent jeopardy. The question, which has hitherto been left unanswered*, yet which must be integrally solved before success could be hoped for, is the following:—To obtain, with a small proportion of fuel, large quantities of fresh, inodorous, salubrious, aerated water, without the help of machinery or the chemical re-agents, by means of a small and compact apparatus, incapable of becoming incrusted, or otherwise going out of

order.

It is to the solution of this difficult and complex problem that I now beg to call attention, and I will proceed to explain the construction of the apparatus by which the object is attained. It is a known: property of steam that it becomes condensed into water again whenever it comes in contact with .water at a temperature lower than itself, no matter how high the temperature of that condensing water may be. It is known that the sea and other natural waters are saturated with air containing a larger proproportion of oxygen and of carbonic acid than exists in the air we breathe. Experiments which I undertook several years ago, with a view, to,determine that amount, shewed me that whilst ordinary rain water contains, on an average, about 15 cubic inches of oxygenised air per gallon' (of which 15 cubic inches of air per

gallon, about six cubic inches are carbonic acid), sea water, owing to the various substances which it holds in solution, contains only, on an average, about 5 cubic inches of oxygenised air per gallon, of which 5 cubic inches about 0.6 or 0.7 cubic inch are carbonic acid, or, in other words, one gallon of sea water contaius about two-thirds less air than ordinary rain or river water. I have also ascertained that air begins to be expelled from such waters, when the temperature reached about 130°. Fahr. Now, my apparatus consists of two parts—an evaporator and a condenser—-joined so as to form one compact and solid mass, screwed and bolted, without soldering, or brazings of any kind. The evaporator consists of a space which is pervaded by steam-pipes containing steam, and immersed in a certain quantity of sea water, a portion of which is to be evaporated; steam, at a pressure of about, seven pounds, is then admitted into the steam-pipes of the evaporator, which steam-pipes are constantly surrounded by •the sea water to be operated upon, and which thus becomes heated by them. The steam is procured on board of steamers directly from their boilers, and, consequently, at a trifling cost; in sailing ships it is obtained from a small boiler, whicli may or may not be connected with the hearth, galley, or caboose. -

The steam, of the above-mentioned pressure being of course hotter than ordinary boiling water, serves to convert a portion of the water contained in tlie evaporator into ordinary or onpressure steam, which, as it reaches the condenser, .is . resolved therein into fresh water. By thus evaporating water under a slighVpressure, one fire performs double duty, and thus the first condition, that of economy, is completely fulfilled, ibr.'whilst, in the usual way, lib. of coal evaporates 8 or 91bs." of water, the same quantity of coals is thus made to evaporate 16 or 181bs. of water. In fact, lam in a position to prove by actual experiment, that from the same amount of steam or of coals employed, the machine which I have just described will produce double the quantity of fresh: water that Gan be obtained by simple or ordinary distillation, and I may say, that with an apparatus constructed on the same principle, and which was sent to Copiapo, in Chili, not less than 30,000 gallons of fresh water per diem are obtained from the sea.

The steam issuing from the evaporator, and which is condensed by the water in the coadensor, imparts, of course, its heat to the sea water in it, and as this water is admitted cold at the bottom, whilst the steam of the evaporator is admitted to the top of the condensor, the water therein becomes hotter and hotter gradually as it ascends, and when it finally reaches the top, its temperature is about 208° Fahr,

I have already stated that, water begins to part with its air at a temperature of about 130° Fahr., therefore, the greater portion of the air contained in the water which flows constantly and uninterruptedly through the condensor is thus separated, and led through a pipe into the empty space left for steam room within the evaporator, when it mixes with the steam.

Now, as about six gallons of sea water must be discharged for «very gallon of fresh water which is condensed, it follows that the steam in the avaporator, before it is finally condensed, has been in contact with twice as much air as water can take up, the result being a production of fresh water to the maximum of aeration, that is, containing as much air as in pure rain water, whilst, the -.upper part of the condensor being open to the atmosphere, all pressure is thus removed from the apparatus.

This, aeration of the water is a condition of the utmost importance, and, in feet, is a condition which, were it not accomplished, would render the apparatus comparatively useless, even though the other desiderata were fulfilled. Whenthe natural waters supplied to our habitations are obtained from impure sources, as is unfortunately-too Often the case, the evils resulting from their use may in some degree be remedied by putting in practice the recommen-dation--v^u'eh has been sometimes made of boiling such water previous to employing is as, a beverage ; unfortunately r ctlie...vs[ater being thereby deprived of air and of carbomftitiid'is, like .distilled water, though in a less degree, unpalatable, and" vapid, and heavy; it is, in fact of difficult digestion; but there is something worse than that; water which has been boiled, or which has been distilled, by reason of its containing no air, has a great tendency to absorb or take air from the media where it is kept, so that if distilled water,-which contains'no air, be kept in a ship's hold, or in an impure and confined place, it will absorb precisely the quantity of air which it can absorb, namely 15 cubic inches per gallon, and if that air be loaded with organic particles or impure emanations, it will soon become fetid and putrid. Thus water, though distilled, if kept in tainted rooms, will soon become foul. The empyreumatic odour and taste which distilled water always possesses and retains for. a considerable time, is in fact due to the destructive action, of the heated surface of the vessels in which-the water is boiled, on the organic substances which are always floating on the air, or those indescribable particles of dust which are seen playing or moving about in a sunbeam, and which have been dissolved s or taken up by the water before its distillation. That water has the power of absorbing and dissolving organic matter in this way is, of course, ! well known, but it may be illustrated iri a very simple manner, as-follows:—-If water, from whatever source, be distilled, the distillnte will, - of course .be fresh water, pure fresh .water, but it will have a peculiar,- nauseous, empyreumatic taste and odour, stronger iv proportion as the heat applied to evaporate it has been more elevated ; it is that smell and taste which render it undrinkable for a while. If, when it has become sweet again by long standing, which period may be hastened by agitation in the atmosphere; if, I repeat it, that distijjed water be then redistilled, the distillate will be found to have acquired again the same empyreumatic taste, and odour as when it was first distilled. How is this ? Because it will by standing or agitation, have re-dissolved a portion of the air in the room in which it was kept, and along with that air it will have absorbed whatever substances were present,'dissolved or suspended in it, and those substances by their contact with the heated surfaces of the still, yield au empyreumatic product, which taints the distillate. The only condition necessary for distilled water not to become putrid or offensive is to saturate it with pure air, because "in that case there is no room left for other gases to impregnate it, at least practically speaking, and in the ordinary conditions of domestic or of ship economy. On board ships, the water which is stored in for the use of the crews in the usual way, in the course of 'about a fortnight becomes putrid and almost -undrinkable, because the oi'ganic matter, which that water contains is undergoing a course of putrefactive fermentation. But about a month or so afterwards the water gradually bcoomes sweeter and sweeter, until at

last it becomes drinkable again; because, eventually, all the organic matter which it contained becomes decomposed, carbonic acid aud water being the result, and although the air- of the ship's hold is noue of the sweetest, the water, produced as just said, remains for ever afterwards perfectly good and palatable, because it is saturated with pure air, and therefore cannot absorb that of the atmosphere.

Now, Dr. Stenhouse, several years ago, I be* lieve, found that the power which charcoal pos* sesses of purifying tainted air is owing to its burning in an insensible manner the substances to which its bad odour was due; and acting upon that discovery of Dr. Stenhouse/ I found that charcoal has the power of destroying the empyreuma of distilled water, when such water is aSrated, that is to say, when it contains atmospheric air, or oxygen. I found by experiments, carried on upon a somewhat extensive scale for many months, that two cubic feet of charcoal are sufficient to remove entirely the empyreutnatic odour and taste of distilled water produced at the rate of 500 gallons per diem, and that the charcoal never wants renewing, because it does'not act as a filter, but as a burner, the substance-burnt'toeing the empyreumatio product, and the result of the slow combustion thereof being carbonic acid and water. I have every reason to believe, from the length of ti_ie : during which several of my apparatus have, been in operation, that such a filter once made will last for ever, because the charcoal disinfects the water, so to speak, as it does air, not Jjy mechanical separation, but by actual though insensible combustion. The water, as it issues from the apparatus, is perfectly sweet, tasteless, inodorous, and completely saturated with a maximum quantity of pure air; it is of sparkling clearness, and being refrigerated in traversing the coiled pipe surrounded by the cold sea water at the" lowest part of the apparatus, it is fit for immediate use.

And thus is the second condition, that of aeration, of digestibility, of wholesomeness, accomplished, whereby the water so produced is at once drinkable, and so sweet and fresh that it cannot be distinguished from the very,.best spring water.

I have already stated that sea water contains a certain quantity of salt in the proportion of about lib. of salt to 331bs. of water. Now, when sea water is evaporated, all the steam produced therefrom being, of course, '■freshwater, all the-salt .which'-that water contained* is left behind: that is to say, the salt previously contained in the evaporated portion if left in that portion which is not yet, evaporated, and which , is, thereof, more impregnated- with- salt than before. If this salt be not removed, and the evaporation is continued, it goes on abcumulating, furring, and imrustin£the vessel, and very soon destroys it. This is, in fact, an inconvenience common, not only to all the . sea water stills hitherto contrived, but to the boilers of marine engines ; for no boiler or vessel is safe from incrustatiou as soon as about half of the sea water admitted in them has been evaporated; that is, when the sea water has been saturated by concentration so as to contain 1 lb. of salt in about 16 lbs. of water.

- My apparatus is not liable to these incrustations or deposits of salt, because the sea water circulates in it in a constant and uninterrupted manner,- and the quantity evaporated (one sixth) is much les3 than is necessary to interfere with the perfect solution of the whole of the salt, since the discharged water contains only about one half per cent, more salt after than before being-operated upon ; that is to say, the sea water, as it is admitted into .the apparatus, contains, as we said, about 16 oz. of. salt in 33 lbs. of water, which is an insignificant increase. On the other" hand, the different parts of the apparatus bsing made of stout iron plates, riveted, and connected in a substantial manner by "screws and bolts, without s 1 lering or brazing of any-kind or in any part, it is perfectly impossible that it should go out of order by any kind of accident short of those cases ot force majeure which, unfortunately, are too often the. cause of the ruin or wreck of the ship itself.

.^foa^-this,^ brief description of my Patent Marine Fresh Wafer Apparatus, it may be, conceived that, by heatiri^the.- Sea-water^t-<mly;.-; 212° Fahr. by means of steam at only a few pounds above atmospheric pressure, it is volatilised in a most economical manner, and is perfectly free from the saliue or organic matters which usually impart to it, in other arranger ments, a nauseous odour and disagreeable tasie; and that the cheapness and small volume ofthe apparatus, the large quantity of fresh^salubrious, arid aerated water which it produces * at an extremely small cost, its absolute safety, permanent order, and the ease ,with which all its parts can be reached, not only render it pre-eminently suited to mai iue purposes, but that it is likewise admirably adapted to such stations or places as are deficient in one. of the first necessities of life, salubrious fresh water, or where it either cannot be obtained at all, or only in an insufficient, precarious, or expensive manner.

* An apparatus's feet high, 3 feet long, and 1£ feet wide, produces 2-1 gallons of fresh water per hour.

Ministers and their Detractors. — The Times professes a belief that ministers are simply bent upon the retention of place; If they oppose a measure coining from the liberal side, which they regard as opposed to the honor and interests of the country, they are denounced as illiberals, obstructives, unworthy of place or public confidence. If they dismiss narrow considerations, and by acting in the spirit of the times, get rid of vexatious questions which have too long divided well-meaning men, they are condemned as weathercocks, and declared unworthy of respect or support. Now try The Times newspaper by its own test, .try Lord Palmerston and one-half of his adherents by it, what must needs be the issue ? The moon is not more changeable than The Times, and Lord Palmerston has boxed the compass of inconsistency. There seems to be a small chance of ousting Lord Derby by interested attack, from such tainted quarters.— Carlisle Patriot.-

Advantage of Habit.-—Bulwer worked his way to eminence—worked it through failure, through ridicule. His facility is only the result of practice and study. He wrote at first very slowly and with great difficulty; but he resolved to master the stubborn instrument of thought, and mastered it. He has practised writing as an art, and, has re-written some of his essays (unpublished) nine or ten times over. Another habit will show the advantage of continuous application. He only works about three hours a day —from ten in the morning till one —seldom later. The evenings, when alone, are devoted to reading, scarcely ever to writing. Yet what an amount, of good hard labor has , resulted from. these, .three - hours! He writes very rapidly, averaging twenty, pages per day of novel print. ...