PHYSICAL.
The lower Mississippi is among the muddiest streams in the world. During the average year it brings down 7,500,000,000 cubic yards of sediment, discharging it along the lower course, or pushing it into the Gulf. As one thinks of the small amount of sediment held in a gallon or two of river water, a comprehension of this vast amount of silt is impossible. It is enough to cover a square mile in area to a depth of 268 feet. In five hundred years it would build above the sea level a State as large and as high as Rhode Island. Thus, by means of this sediment, the river has pushed its mouths fifty miles into the sea, confining its flow within narrow strips of land—natural levees made by the river itself.
The Mississippi is notable for its varying length. Within the memory of the oldest pilot the length of the river between St. Louis and New Orleans has varied more than one hundred and fifty miles, being sometimes longer and sometimes shorter, as the year may be one of drought or of excessive rainfall. Occasionally the river will shorten itself a score of miles at a single leap. The shortening invariably takes place at one of its long sinuous curves for which it is so remarkable. At a season when the volume of water begins to increase, the narrow neck of the loop gives way little by little under the continuous impact of the strengthening current. Narrower and narrower it grows as the water ceaselessly cuts away the bank. Finally the barrier is broken; there is a tumultuous meeting of waters; the next steamboat that comes along goes through a new cut; and a moat or ox-bow lake is the only reminder of the former channel.[5]
In 1863 the city of Vicksburg was situated on the outer curve of such a loop. At that time General Grant and his army were on the opposite side of the river, and the whole power of the Federal government was directed upon devising how the army might cross it and capture the long-beleagured city. So an army engineer conceived the idea of turning the river around the rear of the army. Accordingly, a canal was cut across the loop, in order to make an artificial channel through which its current might run. But the river steadfastly refused to accept any channel it had not itself made, and the ditch soon silted up. Twelve years or more afterward there was trouble; for the river, which had all this time so persistently ignored the canal, one stormy night, when its current was considerably swollen, took a notion to adopt the canal that it had so long refused. Next morning the good people of Vicksburg woke to find their metropolis, not on the river channel, but practically an inland town overlooking a stagnant mud flat. The town of Delta, which, the night before, was three miles below Vicksburg, was, in the morning, two miles above it. Since that time, energy and intelligence have conspired in its behalf, and Vicksburg is still an important river port; but the channel of the river is persistent, and constant effort and watchfulness alone keep a depth of water sufficient for the needs of navigation before the wharves.
The average inhabitant of the flood plain of the Mississippi is not surprised at this capriciousness of the river, for long experience has taught him to look for it. During seasons of mean or of low water, there is little or no trouble; but when floods begin to swell the current, then it is high time to be on the alert, for no one knows what a day or even an hour may bring forth. Perhaps a snag, loosened from the bank above, may come floating down the stream. It strikes a shallow place somewhere in the river, and thereupon anchors in mid-channel. Directly it does, a small riffle or bar of silt will form around it, and this, in turn, sends an eddying current over against the bank. By and by the latter begins to be chipped away, little by little. Perhaps the corrosion of the bank might not be noticed except by a bottom land planter or a riverman. But there is no time to be lost. If some unfortunate individual happens to possess belongings in that vicinity, he simply lays aside his coat and works as if he were a whole legion doing Cæsar's bidding; he well knows that in a very few hours the river will be swallowing up his real estate at the rate of half an acre to the mouthful. It is certainly hard to see one's earthly possessions disappear before the angry flood of the river, but the bottom land planter does not complain, because the experience of generations has taught him that he must expect it. A queer fortune befell Island No. 74.
Between the States of Arkansas and Mississippi there is a large island, which, for want of a name, is commonly known as Island No. 74.[6] This slip of insular land is probably the only territory within the United States and not of it, for this island is without the boundaries of either State, county or township. It is not under control of the government, because it is in the possession of an owner whose claim is acknowledged by the government. The anomalous position of the island as to political situation is due to the erosion of the river as an active and the defects of statutory law as a passive agent. According to the enactment whereby the States of Arkansas and Mississippi were created, the river boundary of the former extends to mid-stream; that of the latter to mid-channel. Herein is the difficulty. A dissipated freshet turned the current against the Mississippi bank, and shifted the former position of mid-channel many rods to the eastward, so that the fortunate or unfortunate owner found his possessions lying beyond both the mid-river point of Arkansas and the mid-channel line of Mississippi. The owner of the plantation may be unhappy at time of election, for he is practically a non-resident of any political division. His grief, however, is somewhat assuaged when the tax gatherer calls, for, being outside of all political boundaries, he has no taxes to pay.
Within a few years the town of Napoleon, which has already been mentioned as the site which beheld the cross erected by Marquette and the seizure of La Salle, was the scene of still another chapter in history. Almost two hundred years from the time when Joliet and Marquette beheld the historic ground, the river turned its current against the banks, and in a few hours the crumbling walls of an old stone building, half a mile or more from the river banks, were the surviving monument that marked the former location of the town.
The Mississippi is indeed a grand study, and the people who have lived in its valley during past ages have seen the river doing just what it is doing to-day; and as race has succeeded race, each in turn has seen the landmarks of its predecessors swept away by its angry flood and buried beneath its sediment. Ever since the crests of the Appalachian and Rocky Mountains were thrust up above the sea, the river has been wearing them away, and bearing the scourings to the vast plain below. In the time of its building it has made the greatest and the richest valley on the face of the earth; next to that of the Amazon it is the largest, covering an area of one and one-quarter million square miles. The river and its tributaries drain twenty-eight States and Territories—an area equal to that of all Europe except Russia. This basin includes half the area of the United States, exclusive of Alaska. It is five times as large as Austria-Hungary, six times the size of France or Germany, nine times the area of Spain, and ten times that of the British Isles. Measured by its grain-producing capacity, this valley is capable of supporting a larger population than any other physical region on the face of the earth. Already it is the foremost region in the world in the production of grain, meat and cotton. The rich soil, sedentary on the prairie and alluvial in the bottomlands, is almost inexhaustible in its nutritious qualities. The soil cannot be "worn out" in the bottomlands, for nature restores its vitality by bringing fresh supplies from the highlands as fast or faster than the seed crop exhausts it. Sixty bushels of wheat or two bales of cotton may be harvested from an acre of bottom lands. So vast in proportions is the yearly crop of food stuffs that more than three hundred thousand freight cars and about two thousand vessels are required to move the crop from farm to market. One hundred and twenty-five thousand miles of railway, fifteen thousand miles of navigable water, exclusive of the Great Lakes, and several thousand miles of canals are insufficient to transport this enormous production; thousands of miles of railway are therefore yearly built in order to keep pace with the growth of population and the settlement of new lands. To the natural resources of the soil add the enormous mineral wealth hidden but a few feet below the surface, and wonder grows to amazement. Coal fields surpassing in extent all the remaining fields in the world; iron ore sufficient to stock the world with iron and steel for the next thousand years; copper of the finest quality; zinc, lead, salt, building stone and timber, all in quantities sufficient for a population a hundred times as great. Is it strange that wise economists point to this territory and say, "Behold the future empire of the world"? Where in the wide world is another valley in which climate, latitude and nature have been so liberal?
It is only a few years since the Indian and the bison divided between them the sole possession of this region. What a change hath the hand of destiny wrought! What a revelation, had some unseen hand lifted the curtain that separated the past from the future! Iron, steam and electricity have in them more of mysterious power than ever oriental fancy accredited to the genii of the lamp, and the future of the basin of the Mississippi will be a greater wonder than the past.
The feast of La Salle was the death warrant of the Indian, and the Aryan has crowded out the Indian, just as the latter evicted the mound builder—just as the mound builder overcame the people whose monuments of burned brick and cut stone now lie fifty feet below the surface. Only a few centuries have gone by since these happenings; can we number the years hence when rapacious hordes from another land shall drive out the effete descendants of the now sturdy Aryan?
(To be continued.)
Read May 17, 1890, before the Engineers' Club of Philadelphia.
Estimated at from 100,000 to 150,000 years. Such estimates, however, are but little better than guesses.
From the best information I can gather I am unable to decide to my own satisfaction whether or not La Salle discovered the Red River. It is not improbable that he never saw this stream, for it is more than likely that at that time, Red River poured its waters directly into the Gulf of Mexico, through Atchafalaya and Cocoudrie Bayous. That these were formerly a part of the channel of Red River, there can be no doubt. The sluggish swale that now leads from the river to the Gulf is a silted channel that was formerly large enough to carry the whole volume of Red River. Such changes in the channel of a river, when the latter flows through "made" soil, are by no means infrequent. It is only a few years since the Hoang River, "the sorrow of Han," broke through its restraining banks, and poured its flood into the Gulf of Pe-chee-lee, 350 miles distant from its former mouth.]
"The bed of the river is so broad that the channel meanders from side to side within the bed, just as the bed itself meanders from bluff to bluff; and, as by erosions and deposits, the river, in long periods of time, traverses the valley, so the channel traverses the bed from bank to bank, justifying the remark often heard, that 'not a square rod of the bed could be pointed out that had not, at some time, been covered by the track of steamboats.'"—J.H. SIMPSON, Col. Eng., Brevet Brig.-Gen., U.S.A.
One of the most noteworthy examples of these cut-offs is Davis'. This cut-off occurred at Palmyra Bend, eighteen miles below Vicksburg. The mid-channel distance around the bend was not far from twenty miles; the neck was only twelve hundred feet across. The fall of the river, measured around the bend, was about four inches per mile; the slope, measured across the neck, was about five and one-half feet, nearly twenty feet per mile. Inasmuch as the soil in the neck was wholly alluvial, the current cut its new channel with exceedingly great rapidity, soon clearing it out a mile in width and more than one hundred feet in depth. The water rushed through the channel with such a velocity that steamboats could not breast its flow for many weeks, while the roaring of its flood could be heard many miles away. The influence of the cut-off was felt both above and below Vicksburg for several years after. The rate of erosion has been perceptibly increased above Vicksburg: and it is not unlikely that the cut-off which occurred a few years later at Commerce, about thirty miles below Memphis, was a result of Davis' Cut. Other recent cut-offs have occurred near Arkansas City, below Greenville, near Duncansby, below Lake Providence at Vicksburg, and at Kienstra. The latter place is below Natchez; all the others are between Natchez and Memphis. A double cut-off is strongly threatened at Greenville.
For convenience to navigation, the islands in the lower Mississippi, beginning at St. Louis, are numbered. Many of them, however, have local names by which they are frequently known.
FREEZING MIXTURES.
The following selection of mixtures causing various degrees of cold, the starting point of the cooling being indicated in the first column, will probably serve many purposes. It should be stated that the amount of depression in temperature will practically be the same, even if the temperature to start from is higher. Of course in the case of snow it cannot be higher than 0° C. (32° F.) But in some cases it is necessary to start at a temperature below 0° C. For instance, the temperature of -49° C. may be reached by mixing 1 part of snow with ½ part of dilute nitric acid. But then the snow must have the temperature -23° C. If it were only at 0° C., the depression would be only to about -26° C.:
| Substances to be mixed in parts by weight. | The temperature sinks | ||||
|---|---|---|---|---|---|
| from | to | ||||
| 1. | Water. | 1 | } | +10° C. | -15.5° C. |
| Ammonium nitrate. | 1 | ||||
| 2. | Dil. hydrochloric acid. | 10 | } | +10 | -17.8 |
| Sodium sulphate. | 16 | ||||
| 3. | Dil. hydrochloric acid. | 1 | } | +10 | -16 |
| Sodium sulphate. | 1½ | ||||
| 4. | Snow. | 1 | } | + 0 | -32.5 |
| Sulphuric acid. | 4 | ||||
| Water. | 1 | ||||
| 5. | Snow. | 1 | } | - 7 | -51 |
| Dil. sulphuric acid. | 1 | ||||
| 6. | Snow. | 1 | } | -23 | -49 |
| Dil. nitric acid. | ½ | ||||
| 7. | Snow. | 1 | } | 0 | -17.8 |
| Sodium chloride. | 1 | ||||
| 8. | Snow. | 1 | } | 0 | -49 |
| Calcium chloride. | 1.3 | ||||
| 9. | Snow. | 1 | } | 0 | -33 |
| Hydrochloric acid. | 0.625 | ||||
| 10. | Snow. | 1 | } | 0 | -24 |
| Sodium chloride. | 0.4 | ||||
| Ammon. chloride. | 0.2 | ||||
| 11. | Snow. | 1 | } | 0 | -31 |
| Sodium chloride. | 0.416 | ||||
| Ammon. nitrate. | 0.416 | ||||
THE APPLICATION OF ELECTROLYSIS TO QUALITATIVE ANALYSIS.
By CHARLES A. KOHN, B.Sc., Ph.D., Assistant Lecturer in Chemistry, University College, Liverpool.
The first application of electrolysis to chemical analysis was made by Gaultier de Claubry, in 1850, who employed the electric current for the detection of metals when in solution. Other early workers followed in this direction, and in 1861 Bloxam published two papers (J. Chem. Soc., 13, 12 and 338) on "The application of electrolysis to the detection of poisonous metals in mixtures containing organic matters." In these papers a description is given of means for detecting small quantities of arsenic and of antimony by subjecting their acidulated solutions to electrolysis. The arsenic was evolved as hydride and recognized by the usual reactions, while the antimony was mainly deposited as metal upon the cathode. The electrolytic method for the detection of arsenic, in which all fear of contamination from impure zinc is overcome, has since been elaborated by Wolff, who has succeeded in detecting as little as 0.00001 grm. arsenious oxide by this means (this Journal, 1887, 147).
In a somewhat different manner the voltaic current is made use of in ordinary qualitative analysis for the detection of tin, antimony, silver, lead, arsenic, etc., by employing a more electro-positive metal to precipitate a less electro-positive one from its solution.
The quantitative electrolytic methods of analysis, some of which I had the honor of bringing before the notice of the Society some time back (this Journal, 1889, 256), have placed a number of methods of determination and separation of metals in the hands of chemists, which can be employed with advantage in qualitative analysis, especially in case of medical and medico-legal inquiry. These methods are not supposed to supersede in any way the ordinary methods of qualitative analysis, but to serve as a final and crucial means of identification, and thus to render it possible to detect very small quantities of the substances in question with very great certainty. As such they fulfill the required conditions admirably, being readily carried out, comparatively free from contamination with impure reagents, and capable of being rendered quantitative whenever desired.
In conjunction with Mr. E.V. Ellis, B.Sc., I have examined the applicability of the electrolytic methods for the detection of the chief mineral poisons (with the exception of arsenic, an electrolytic process for the detection of which has already been devised, as described), viz., antimony, mercury, lead, and copper.
Antimony.—The method employed in the case of antimony is that adopted in its quantitative estimation by means of electrolysis, a method which insures a complete separation from those metals with which it is precipitated in the ordinary course of analysis—arsenic and tin. This fact is of considerable importance in reference to the special objects for which these methods have been worked out.
The precipitated sulphide is dissolved in potassium sulphide, and the resultant solution, after warming with a little hydrogen peroxide to discolorize any poly-sulphides that may be present, electrolyzed with a current of 1.5-2 c.c. of electrolytic gas per minute (10.436 c.c. at 0° and 760 mm. = 1 ampere), when the antimony is deposited as metal upon the negative electrode. One part of antimony (as metal) in 1,500,000 parts of solution may be thus detected, a reaction thirty times more delicate than the deposition by means of zinc and potassium. The stain on the cathode, which latter is best used in the form of a piece of platinum foil about 1 sq. cm. in diameter, is distinct even with a solution containing 1/28 mgrm. of antimony; and by carefully evaporating a little ammonium sulphide on the foil, or by dissolving the stain in hot hydrochloric acid and then passing a few bubbles of sulphureted hydrogen gas into the solution, the orange colored sulphide is obtained as a satisfactory confirmatory test. The detection of 0.0001 grm. of metal can be fully relied on under all conditions, and one hour is sufficient to completely precipitate such small quantities.
Mercury.—Mercury is best separated from its nitric acid solution on a small closely wound spiral of platinum wire. The solution to be tested is acidified with nitric acid and electrolyzed with a current of 4-5 c.c. (c.c. refer to c.c. of electrolytic gas per minute). The deposition is effected in half an hour. The deposited metal is removed from the spiral by heating the latter gently in a test tube, when the mercury forms in characteristic globules on the upper portion of the tube. As a confirmatory and very characteristic test, a crystal of iodine is dropped into the tube, and the whole allowed to stand for a short time, when the presence of mercury is indicated by the formation of the red iodide. 0.0001 grm. of mercury in 150 c.c. of solution can be clearly detected.
Wolff has applied this test under similar conditions, using a special form of apparatus and a silver-coated iron anode (this Journal, 1888, 454).
Lead.—Lead is precipitated either as PbO2 at the anode from a nitric acid solution or as metal at the cathode from an ammonium oxalate solution. In both cases a current of 2-3 c.c. suffices to effect the deposition in one hour.
Here, again, 0.0001 grm. of metal in 150 c.c. of solution can be easily detected. With both solutions this amount gives a distinct discoloration to the platinum spiral, on which the deposition is best effected. As a confirmatory test the deposited metal is dissolved in nitric acid and tested with sulphureted hydrogen, or the spiral may be placed in a test tube and warmed with a crystal of iodine, when the yellow iodide is formed. This latter reaction is very distinct, especially in the case of the peroxide.
Of the above two methods, that in which an ammonium oxalate solution is used is the more delicate, although it cannot be employed quantitatively, owing to the oxidation of the metal that takes place.
An addition of 1 grm. of ammonium oxalate to the suspected solution is sufficient.
Copper.—0.00005 grm. of copper can be very readily detected by electrolyzing an acid solution in the usual way. A spiral of platinum wire is employed as the cathode, and the presence of the metal confirmed for by dissolving it in a little nitric acid, diluting with water and adding potassium ferrocyanide.
To detect these metals in cases of poisoning, the organic matter with which they are associated must first be destroyed in the usual way by means of hydrochloric acid and potassium chlorate, and the precipitates obtained in the ordinary course of analysis, then subjected, at suitable stages, to electrolysis. As the solutions thus obtained will be still contaminated by some organic matter, it is necessary to pass the current for a longer time than indicated above. On the other hand, urine can be tested directly for these poisons.
The presence of mercury or of copper may be detected by acidifying the urine with 2-3 c.c. of nitric acid (conc.), and electrolyzing as described. 0.0001 grm. of metal in 30 c.c. of urine can be detected thus, or 1 part in 300,000 of urine.
Lead does not separate well as peroxide from urine, but if ammonium oxalate be added, and the lead deposited as metal, the reaction is quite as delicate as in aqueous solution, and 0.0001 grm. of lead can be thus detected.
With antimony it is advisable to precipitate it first as sulphide, but it can be detected directly, though not so satisfactorily, by acidifying the urine with 2-3 c.c. of sulphuric acid (dil.), and electrolyzing with a current of 1-5 to 2 c.c. In this case also it is precipitated as metal upon the cathode (cp. Chittenden, Proceedings Connecticut Acad. Science, Vol. 8).
In the presence of urine it is advisable to continue the passage of the current for about twice the time required in the case of aqueous solutions.
That an approximately quantitative result can be obtained under the above conditions was shown in several cases in which deposition of 0.001 grm. of metal was confirmed with considerable accuracy, the spiral or foil being weighed before and after the experiment.
A comparison of the delicacy of these tests with the ordinary qualitative tests for antimony, mercury, lead, and copper by means of sulphureted hydrogen, showed that the two were equally delicate in the case of antimony and of copper, but that in that of mercury and of lead the electrolytic test was at least eight times the more delicate. These comparisons were made in aqueous solutions. In testing urine the value of the electrolytic method is still more evident, for here the color of the liquid interferes materially with the reliability of the ordinary qualitative tests when only very small quantities of the metals referred to are present.
Beyond the detection of mineral poisons, qualitative electrolysis can only offer attraction to analysts in special cases, and the data on the subject are to be found in the many electrolytic methods already published. Beyond testing for gold and silver in this manner, I have not therefore examined the applicability of these methods further.
The detection of small quantities of gold and silver is of considerable importance, and advantage can be taken of the ease with which they are separated from potassium cyanide solution by the electric current for this purpose.
Silver.—Silver is obtained as chloride in the course of analysis. To confirm for the metal electrolytically, this precipitate is dissolved in potassium cyanide and the resulting solution electrolyzed with a current of 1-1.5 c.c. A spiral of platinum wire is employed as the anode, from which the silver may be dissolved by means of nitric acid, and tested for by hydrochloric acid or by sulphureted hydrogen. 0.0001 grm. of silver in 150 c.c. of solution can be detected thus, and one hour is sufficient for the deposition.
Gold.—Gold is deposited under similar conditions to silver from cyanide solutions. The deposit, which is rather dark colored, can be dissolved in aqua regia and confirmed for by the Cassius' purple test. Here again 0.0001 grm. of metal in 150 c.c. of solution can be detected without any difficulty.
As gold and silver are both extracted from quartziferous ores by treatment with potassium cyanide solution according to the MacArthur-Forrest process of gold extraction (this Journal, 1890, 267), this electrolytic method should prove very useful. By electrolyzing the resulting solution a mixture of gold and silver will be deposited upon the cathode, which can then be parted by nitric acid and tested for as described.