Chapter 9

In Fig. 7, as in Fig. 1, DT is tangent at T to the given circle whose center is O, and at t to the circle about C whose diameter is AB, the major axis. Since DTO is a right angle, T lies upon the circumference of the circle whose center is C, and diameter DO; this circle cuts the asymptote SCS at M and N. The semi-conjugate axis is a mean proportional between D A and AO; now drawing TM and TN, it is seen that Tt is that mean proportional; and a circle described about C with that radius will be tangent to TO. DT, then, is the radius of the circle to be described about the focus of the conjugate hyperbola for its construction according to the enunciation first given: and we observe that DT and TO are supplementary chords in the circle about C through D and O. The conjugate foci must therefore lie upon this circumference, at D' and O'; and since D'O' is perpendicular to DO, D'T will be perpendicular and T'O' will be parallel to SCS.

Now as TO increases, T'O' will diminish, until, when TO equals DO, T'O' will vanish and with it Ct'; and at this crisis, the case is the same as in Fig. 4; but the conjugate hyperbola logically reduces to _two_ right lines, extending from C to infinity on the right and left. As indeed it should from the familiar construction, since the distances from D' and O' to any point on the horizontal axis being equal, their difference is constant and equal to zero.

It appears, then, that a conic section may be defined as the locus of a point which is equally distant from a given point and from the circumference of a given circle. Boscovich defines it as the locus of a point so moving that its distances from a given point and from a given right line shall have a constant ratio.

The latter definition involves the conceptions of a rectilinear directrix, and a varying ratio in the cases of the different curves, this ratio being unity for the parabola, less for the ellipse, and greater for the hyperbola. The former involves the conception of a circular directrix with a ratio equal to unity in all cases; and the two definitions become identical in the construction of the parabola, which is in fact the only curve of which a clear idea is given by either of them. That of Boscovich has been given a prominence far in excess of its merits, being made the foundation for the discussion of these important curves, and this in a textbook whose preface contains the following true and emphatic statement, viz.:

"The abstract nature of a ratio, and the fact that it is a compound concept, peculiarly unfit it for elementary purposes."

The definition herein set forth has not been given in any treatise on the subject, so far as we have been able to ascertain. And it is presented with the distinctly expressed hope that it never will be, except as a mere matter of abstract interest.

Of this it may, like the other, possess a little, but both have the great disadvantage that, except in relation to the parabola, the idea which they convey to the mind of the curves to which they relate, if indeed they convey any at all, is most obscure and indirect; and of practical utility neither one can claim a particle.

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TABLE OF ATOMIC WEIGHTS.

(Issued December 6, 1890.)

By request of the Committee of Revision and Publication of the Pharmacopoeia of the United States of America, Prof. F.W. Clarke, chief chemist of the United States Geological Survey, has furnished a table of atomic weights, revised upon the basis of the most recent data and his latest computations. The committee has resolved that this table be printed and furnished for publication to the professional press. The committee also requests that all calculations and analytical data which are to be given in reports or contributions intended for its use or cognizance be based upon the values in the table. It would be highly desirable that this table be adopted and uniformly followed by chemists in general, at least for practical purposes, until it is superseded by a revised edition. It would only be necessary for any author of a paper, etc., to state that his analytical figures are based upon "Prof. Clarke's table of atomic weights of December 6, 1890," or some subsequent issue.

This table represents the latest and most trustworthy results, reduced to a uniform basis of comparison, with oxygen=16 as starting point of the system. No decimal places representing large uncertainties are used. When values vary, with equal probability on both sides, so far as our present knowledge goes, as in the case of cadmium (111.8 and 112.2), the mean value is given in the table.

The names of elements occurring in pharmaceutical, medicinal, chemicals, are printed in italics[1]:

[Transcriber's Note 1: ITALICS represented by surrounding with "_".]

Name. Symbol. Atomic Weight.

_Aluminum_. _Al_ 27. _Antimony_. _Sb_ 120. _Arsenic_. _As_ 75. _Barium_. _Ba_ 137. _Bismuth_. _Bi_ 208.9 _Boron_. _B_ 11. _Bromine_. _Br_ 79.95 Cadmium. Cd 112. Caesium. Cs 132.9 _Calcium_. _Ca_ 40. _Carbon_. _C_ 12. _Cerium_. _Ce_ 140.2 _Chlorine_. _Cl_ 35.45 _Chromium_. _Cr_ 52.1 Cobalt. Co 59. Columbium.[1] Cb 94. _Copper_. _Cu_ 63.4 Didymium.[2] Di 142.3 Erbium. Er 166.3 Fluorine. F 19. Gallium. Ga 69. Germanium. Ge 72.3 Glucinum.[3] Gl 9. _Gold_. _Au_ 197.3 _Hydrogen_. _H_ 1.007 Indium. In 113.7 _Iodine_. _I_ 126.85 Iridium. Ir 193.1 _Iron_. _Fe_ 56. Lanthanum. La 138.2 _Lead_. _Pb_ 206.95 _Lithium_. _Li_ 7.02 _Magnesium_. _Mg_ 24.3 _Manganese_. _Mn_ 55. _Mercury_. _Hg_ 200. _Molybdenum_. _Mo_ 96. Nickel. Ni 58.7 _Nitrogen_. _N_ 14.03 Osmium. Os 191.7 _Oxygen_.[4] _O_ 16. Palladium. Pd 106.6 _Phosphorus_. _P_ 31. Platinum. Pt 195. _Potassium_. _K_ 39.11 Rhodium. Rh 103.5 Rubidium. Rb 85.5 Ruthenium. Ru 101.6 Samarium. Sm 150. Scandium. Sc 44. Selenium. Se 79. _Silicon_. _Si_ 28.4 _Silver_. _Ag_ 107.92 _Sodium_. _Na_ 23.05 Strontium. Sr 87.6 _Sulphur_. _S_ 32.06 Tantalum. Ta 182.6 Tellurium. Te 125. Terbium. Tb 159.5 Thallium. Tl 204.18 Thorium. Th 232.6 Tin. Sn 119. Titanium. Ti 48. Tungsten. W 184. Uranium. U 239.6 Vanadium. V 51.4 Yterbium. Yb 173. Yttrium. Yt 89.1 _Zinc_. _Zn_ 65.3 Zirconium. Zr 90.6

--_Am. Jour. Pharm._

[Footnote 1: Has priority over niobium.]

[Footnote 2: Now split into neo-and praseo-didymium.]

[Footnote 3: Has priority over beryllium.]

[Footnote 4: Standard, or basis of the system.]

* * * * *

THE TANNING MATERIALS OF EUROPE.

The tanning materials of Europe are of an altogether different type from those of the United States. The population is so dense that the quantity of home materials produced is not nearly proportionate to the amount consumed, and consequently they must draw upon surrounding lands for their supply. The vegetation of these adjacent countries is of a much more tropical nature, and it naturally follows that the tanning materials are also of a different species.

Tanning materials may be divided into two great classes, viz.: Physiological and pathological.

PHYSIOLOGICAL.

The first class includes those tannins which are the results of perfectly natural or normal growth, and a growth necessary to the development of vegetation, for instance, bark, sumac, etc., whereas the second class contains those which are the results of abnormal growth, caused by diseases, stings of insects, etc. An example of this is the gall. Both of these classes are used to a great extent in Europe, while only the first division is in general use in the United States. We will first consider the physiological tannins.

_Oak Bark._--This material was, is, and will be for some time to come the main tanning material in use here in Europe. The advantages of the oak tannage are as fully appreciated here as in the United States. The European oak gives a light colored, firm leather, with good weight results, is comparatively cheap and of an excellent quality. The varieties are numerous, each country having its own kind. Those in most general use are:

_Spiegel Rinde_ (mirror bark).--This bark is well distributed throughout Europe, and is peeled when the tree has attained a growth of from 12 to 24 years. It is marketed in three grades.

_Reitel Rinde_--Is obtained from the same tree as the spiegel rinde, but after the tree has attained a growth of from 25 to 40 years.

_Alte Pische_ (old oak).--Obtained from the aged tree. It is not as valuable as the younger bark, and consequently brings a much lower price.

Spiegel rinde may be judged by small warts which appear on the shining surface of the bark. The presence of a great number of these, as a rule, indicates a high tannin percentage.

Bosnia has fine oak trees, the bark containing 10 to 11 per cent. tannin.

Bohemia has the _trauben eiche_ (grape oak).

France uses the kirmess oak, which grows in the south of that country and in northern Africa. Two grades are made, viz., root and trunk.

Tyrol has the evergreen oak--12 to 13 per cent. tannin.

Sardinia possesses a cork oak, which yields 13 to 14 per cent.

White oak is found throughout Europe, yielding 10 per cent. The price of oak bark varies a great deal. The assortment is much more strict than in the United States. In Austria it brings 4 to 5 fl., equal to $1.60 to $2 per kilo. (224 lb.); in Germany, 11 to 16 marks per 100 kilos.[1]

[Footnote 1: In the principal districts in America, removed from the cities, the price of oak bark is about $4 to $6 per cord or per ton of 2,240 lb. The hemlock bark, which gives a sole leather just as thoroughly tanned, but of a darker and reddish color, costs the larger tanners from $3 to $4 a cord.]

The above mentioned varieties are all used for both upper and sole leather. In Germany a great deal of upper leather is pure oak tannage, but one seldom finds a pure oak tanned sole leather; it is almost always in combination with other tannics.

_Pine Bark_--Is well distributed and is a very important tanning material. It bears the same relation to oak bark here as does hemlock in America, but its effects are quite different from hemlock. The best Austrian sorts are those of Styria and Bohemia, but that of Karuthen is also of good quality. The German pine comes from Thuringia to a great extent. The countries that consume the greatest amount of pine bark are Austria, Germany, Russia and Italy. The tannin contained varies from 5 to 16 per cent. Its use is almost wholly confined to the handlers, as its weight returns are not so satisfactory as oak or valonia. In case it should be used for layers it is always in combination with some better weight-giving tannic. For upper leather its use is limited.

The bark is always peeled from the felled tree, and often the woodman accepts the bark in part payment for his labor; he then sells the bark to the tanner or agents who go about the country collecting bark. It is generally very nicely cleaned. I would here like to correct a mistake which tanners often make in their estimations of the value of barks. A tanner usually buys the bark of southern-grown trees in preference to that of trees grown in northern countries, as it is a common idea that southern vegetation contains more tannin than that of the north. This is a fallacy, as has not only been proved by careful analyses, but may also be found to be an incorrect conclusion after a moments' thought. Those trees which flourish in southern countries grow very rapidly, and as tannin is necessary to the development of leaf structure, etc., it is absorbed to a greater extent than is the case with the slower-growing tree of the north. The tannin contained in the sap does not increase in the same ratio as does the rapid growth, and it follows that the remainder in the bark is less than in the tree of slower growth.

_Birch Bark_--Is at home in Russia, Norway, and Sweden. It is used for both upper and sole leather, but seldom alone. The bark is usually peeled from the full grown tree, and contains 4 to 9 per cent. tannin.

_Willow Bark_--May also be found in the above mentioned countries and also in Germany. This material is used for both upper and sole leather, and contains 6 to 9 per cent. tannin. It is a very delicate material to use, as its tannin decomposes rapidly.

_Erlen Rinde_--Is also a native of Germany, but is not used to any great extent. The same may be said of the larch, although this variety is also to be met with in Russia.

_Mimosa Bark_--Is obtained from the acacia of Australia. It is a favorite in England. The varieties are as follows: Gold wattle, silver wattle (blackwood, lightwood), black wattle, green wattle. The gold wattle is a native of Victoria. Its cultivation was tried as an experiment in Algeria and met with some success. The trees are always grown from seeds. These seeds are laid in warm water for a few hours before sowing. The acacia may be peeled at eight years' growth and carries seeds. The Tasmania bark is very good; that from Adelaide likewise good.

Sydney does not produce so good an article, but Queensland better. The bark is marketed in the stick, ground or chopped.

Madagascar and the Reunion Islands have also a mimosa bark.

The mimosa barks give a reddish colored leather, pump well and contain a high tannin percentage, 10 to 35 per cent.

Now we will consider the fruit tanning materials.

Valonia may truly be called one of the most generally used tanning agents at present employed in Europe. All countries consume it more or less. Valonia was first used in England about the beginning of this century. A few years later Germany began using it, and still later Austria introduced it. It is the fruit of the oak tree and is obtainable in Asia Minor and the adjacent islands. In form it resembles the American acorn, but in size it nearly trebles it. The fruit may be divided into two parts, namely, the cup and acorn, and the cup again divided into trillor and inner cup. The acorn only contains 10 per cent. tannin, whereas the cup contains from 25 to 40 per cent.

The percentage depends altogether upon the time of harvesting and the place of growth. The best valonia is derived from Smyrna, and is naturally the highest priced article. Valonia is worth from 22 to 28 florins ($9 to $11) per 100 kilos. (224 pounds) at present. The other provinces and islands from which it is obtainable are Demergick, Govalia, Idem, Ivalzick, Troy (this is the best); Metelino Island, the vicinity of Smyrna. The material sold in three grades--prime, mazzano; seconds, una aqua; thirds, skart.

The product of Smyrna generally averages:

Tons. Price. Prime. 2,000 to 3,000 28 florins. Seconds. 5,000 to 10,000 25 " Thirds. 20,000 to 30,000 22 "

The _Metilino_ valonia is a product of a neighboring island, and is a very good article. It may be easily distinguished by its thin cup. It is harvested in September.

The _Candia_ valonia is nearly as long as it is wide, in contrast to the Smyrna, which is much wider than long. The recent harvest showed a return of 800 to 1,000 tons, but no assortment is made. A grade called the Erstlige is sold, this being the first which has fallen to the ground before maturing.

A peculiarity of the valonia is that it often strikes out a sort of sugar sweat, which gives the cup a less attractive appearance, but denotes the presence of large quantities of tannin.

Valonia is used almost wholly for sole leather, either alone or in combination with pine or oak bark or knoppern and myrabolams. The union of valonia and knoppern is that in most general use. Valonia gives the leather a yellowish appearance, as it deposits a great deal of yellow bloom. The leather is very firm and of good wearing qualities. The weight results are also excellent, as will be seen below. To sole leather there are usually given from one to three layers of valonia. The demand for valonia is increasing more and more every year, and the present outlook does not indicate any relaxation of its popularity. Its use for upper leather is very limited.

Myrabolams are mainly used in England and Austria, and give a nice light-colored leather, both upper and sole, although rarely used alone. Their main use is for dyeing purposes. They are indigenous to the East Indies.

Sumac is so well known that treating of it is superfluous. Its use is very extensive, and it is a general favorite for light, fine leather, which is mostly used for colors.

_Gambier_--Is in general use in England and to some extent in Germany.

_Catechu_.--Obtained from India, resembles gambier greatly. Its use is almost wholly confined to England. It is also consumed by the silk manufacturers in preference to gambier, for weighting purposes.

PATHOLOGICAL.

We now leave the physiological class and take up those tanning materials included in the pathological class, or those of abnormal growth.

_Galls_.--These are not consumed to any great extent at the present period, but formerly they were used quite extensively. The galls are found upon the leaves of the oak or sumac, etc. The direct cause of their growth is that a certain wasp (cynips galles) stings into the leaf and after depositing its egg, flies away. The egg develops into a larva and then into a full-fledged wasp, boring its way out of the gall which has served as a protection and nourisher. This accounts for the hole noticed in almost every gall. The different varieties include Aleppo. It is found upon the same trees as the valonia and contains 60 to 75 per cent. tannin; Istrian galls, 32 per cent. tannin; Persian, 28 to 29 per cent. tannin. Chinese galls, giving 80 to 82 per cent. tannin, are the results of the sting of a louse, and make a very light-colored leather. The dyers also use this material for coloring.

_Knoppern_--Belongs to the family of galls, and is a most important factor of commerce in Austria. The knopper is generally found on the acorn or leaf of the oak tree. The greatest quantity is derived from the steel oak of Hungary. The tannin contained varies from 27 to 33 per cent. Knoppern are not being used so much now as formerly, and consequently the amount harvested lessens from year to year. Its main use was and is in combination with valonia as layers for sole leather. Valonia gives better weight results than knoppern, and is replacing knoppern more and more every year. The combination of knoppern, valonia and myrabolams is also quite popular, and gives good results. Knoppern are seldom used alone, being generally combined with some other tannin. Austria is almost the only consumer at present, but Germany used it extensively formerly.

_Bark and Wood Extracts_--Are becoming general favorites throughout Europe, partly because of their weight-giving qualities and partly as the transportation costs so little; they can be used to strengthen weak bark liquors.

_Oak Extracts_--Are well liked, both wood and bark, and are used extensively. Slavonia furnishes a great deal of it.

_Chestnut Oak Wood Extract_--Is manufactured in quantities, and easily finds purchasers.

_Pine Bark Extract_--Is also consumed in goodly amounts.

_Quebracho Wood Extract_.--The wood is shipped from Brazil to Hamburg and other ports, and the tannin extracted there. Hamburg furnishes quantities of it.

_Hemlock Extract_--Is used in Russia, and seems to have taken a hold on the shoe buyers' fancies, as they now make imitations of it in color. The hemlock that is consumed is imported from America.

As most leather is sold by weight in Europe, the leather manufacturers aim to obtain as good weight results as possible, and often, I am sorry to say, do so at the sacrifice of quality. This is common to both upper and sole leather. Sole leather is nine times out of ten given false weight by forcing entirely foreign substances into the leather, such as glucose, barium chloride, magnesium chloride, resins, etc. Glucose and resin are also used for weighting upper leather. Leather is also weighted with extracts by overtanning. Leather buyers have become very wary of late and do not purchase large quantities before an analysis is made of a fair sample.

One more word before I close. The governments and private individuals in Europe cultivate and raise trees for both lumber and bark purposes. The forests are excellently cared for by efficient foresters, and the result is that the tanners obtain much cleaner and better bark, and of a very even quality. Would it not be a good idea if some individual, who would certainly earn the everlasting gratefulness of the tanners, would look into this matter, and see that not only the lumber side of our forest cultivation is not neglected, but that the bark also is preserved and cared for? Of course, we can obtain all the bark necessary at present and for some time to come, but the time will come when we shall certainly regret not having taken these steps, if the lumbermen and bark peelers go on devastating magnificent forests. Below will be found a table of weight results. Sole leather tanned with these materials gives for every 100 lb. green hide the following quantities of finished leather:

lb. Oak bark 48 to 54 " extract 55 to 56 Pine bark 44 to 46 " extract 48 to 50 Willow 45 to 46 Birch bark and oak extract 49 to 51 Quebracho wood and extract 48 to 49 Valonia 52 to 56 Knoppern 51 to 53 Myrabolams 50 Knoppern, myrabolams and valonia 52 to 53 Hemlock 55

Specification of tanning materials used in different countries:

_France_. Oak bark (kirmess). Sumac. Chestnut wood extract. Quebracho " " Some gambier.

_Italy_. Oak bark. Pine " Sumac. Valonia.

_England_. Oak bark. Divi divi. Myrabolams. Valonia. Mimosa. Extracts { Oak bark and wood hemlock. Gambier. Cutch.

_Germany and Austria_. Oak bark. Pine " Willow bark. Valonia. Knoppern. Myrabolams. { Oak bark and wood. Extracts { Pine bark and wood.

_Russia._ Birch bark. Willow " Oak " Pine " Hemlock extract.

_Norway and Sweden_. Birch bark. Willow " Oak "

WALTER J. SALOMON. --_Shoe and Leather Reporter_.

* * * * *

AN APPARATUS FOR HEATING SUBSTANCES IN GLASS TUBES UNDER PRESSURE.[1]

[Footnote 1: Read at the meeting of the Chemical Section of the Franklin Institute held March 17, 1891.]

By H. PEMBERTON, Jr.

Chemists who do not happen to have in their laboratories oil or air baths for heating closed tubes can make an air bath at short notice from materials furnished by all dealers in steam fittings.

_Order_: