was closed and the bulb disconnected and lowered into a solution of hydriodic acid of approximately known strength, obtained by acidifying potassium iodide with hydrochloric acid. When the desired amount of liquid had been drawn in, the stop-cock was closed and connection made with the carbon dioxide, by which all residual air was expelled. Then the bulb, held so as to prevent the escape of the liquid, was again exhausted by attachment to the pump. After about 10cm3 of nitric oxide were admitted, attachment was made to the receiver containing the oxygen, which was allowed to enter slowly under the diminished pressure within the bulb, and with continous shaking of the contents of the latter. The latter precaution is essential to the process, as otherwise there is imperfect distribution of the hydriodic acid and the danger of forming nitric acid. But when the solution of hydriodic acid is kept strong and the shaking continued while the oxygen enters and for a minute or two afterward, depending on the rapidity with which it was admitted, the oxygen may be allowed to enter quite rapidly without any fear of imperfect action. The oxygen being immediately utilized, the partial vacuum is effected only by the heat generated, which is scarcely noticeable. As a rule the bulb and contents were well cooled before the oxygen was admitted.

It is necessary of course to prevent the access of air into the bulb until the acid has been neutralized, to accomplish which, without loss of iodine, potassium carbonate must be used, at least for the end reaction. To remove the contents of the bulb for titration, the two delivery tubes were filled with water, after removing all sodium hydrate from the one through which the oxygen was entered; the shorter end connected to a supported funnel containing a saturated solution of bi-carbonate and the longer one inserted into an Erlenmeyer beaker containing a saturated solution of bicarbonate in amount sufficientas previously determined-to neutralize all the acid taken. By opening that stop-cock the delivery tube of which reaches below the liquid in the beaker, the bi-carbonate is drawn in by the partial vacuum, with liberation of sufficient carbon dioxide. to force all the liquid out. Owing to the consequent effervescence as the liquid gains its exit, the flow must be regulated by the stop-cock so as to avoid loss of iodine, which is prevented by inclining the beaker so that the bubbles strike against its side instead of being allowed to splatter out of the opening. To wash out the bulb, it is raised almost horizontally, so as to prevent the liquid from running through, and the upper stopcock opened to admit the bicarbonate from the funnel. Both stop-cocks are then closed, the bulb disconnected and agitated, after which it may be washed with water and admission of air

without any fear of liberating more iodine. An excess of decinormal arsenic is then run into the beaker and titrated back with iodine.

The many little precautions essential to note for the manipulation are in practice accomplished in a few moments. Seven determinations (not counting one which was all but completed, when an accident terminated it) from the weighing of the perchlorate to the titration, were completed in one day; and the results recorded in Table VII show with what reliability. In making the series of experiments recorded in Table VII, it was found expeditious to have a partial vacuum always accessible instead of waiting each time for the exhaustion. This was obtained by connecting a vacuum flask with a two-holed stopper to an ordinary water pump, and having the other perforation fitted with a glass stop-cock. The bulb was merely attached to the vacuum by a piece of rubber tubing; the stopcock opened and closed immediately, by which means a sufficient exhaustion was secured. To have the vacuum always in readiness a valve, described in a former article of mine, was placed in the rubber leading to the pump, and when lubricated with glycerine would hold the vacuum perfectly. The nitric oxide employed was supplied by a Kipp generator, in which globules of copper were acted upon by nitric acid mixed with an equal volume of water. To purify the gas evolved from any possible trace of the higher oxides, it was first passed through an acidified solution of potassium iodide in Geissler absorption bulbs, the latter one of the three being alkaline. This method of generating nitric oxide in a Kipp generator (preferably charged with dilute acid and kept warm by immersion in hot water when large amounts of the gas are to be drawn at frequent intervals) was devised by Professor Gooch, by whom it has been employed for some time. It is automatic and eminently satisfactory. The hydriodic acid was obtained from a solution of potassium iodide containing one gram in ten cubic centimeters; thirty cubic centimeters being taken for each experiment, and acidified with the required amount of hydrochloric acid immediately before using, so as to prevent any liberation of iodine by the oxygen of the air. In those experiments in which more than this amount of potassium iodide was employed a correspondingly stronger solution of the latter was used, so that the volume of water was in all cases thirty cubic centimeters.

*This Journal, 1, p. 132.

In experiments (40) and (43) during a momentary pause in the shaking of the bulb during the absorption, a black deposit of iodine began to form on the glass, and the result proves the importance of the precaution previously given, that the hydriodic acid should be kept hurling about the bulb until the action is completed. The blank determination (45) shows a constant error of the process which is about 0.0003+ and will be seen to correspond very closely to the average error of the determination. The cause is doubtless to be attributed to the trace of air which may remain in the bulb or be dissolved in the water. Since it can easily be determined and the correction made, it does not detract in any degree from the reliability of the determination.

To determine perchloric acid associated with other oxidizing agents it is only necessary to treat the mixture with the reagents which this investigation and the one referred to has shown to accomplish the reduction without affecting the perchlorate; subsequently evaporating to dryness and treating the residue according to the above process, viz., by heating in a current of carbon dioxide until decomposition is complete; collecting the oxygen over caustic potash; allowing it to enter a partial vacuum bulb containing a solution of potassium iodide, hydrochloric acid and nitric oxide under constant agitation; and determining by means of a standard solution of arsenic the amount of iodine set free. The method is proving applicable also to the determination of oxygen in air or wherever it may be obtained in the free state, unless diluted to such an extent with other gases that the vacuum would be filled by the diluent; even this contingency could be met by enlargement of the absorption bulb.

Many helpful suggestions are to be credited to Professor Gooch.

ART. XXXI.-On an Occurrence of Copper in Western Idaho; by R. L. PACKARD.

THE Seven Devils is the name (of rough frontier origin) given to a range or group of mountains on the extreme western border of Idaho where that state is separated from Oregon by the Snake River on its northerly course to empty into the Columbia. The river runs through a deep gorge as it passes the mountains, the east side of which is formed by members of the Seven Devils group, while the western side or wall, which is very precipitous, is formed by a range on the Oregon side called the Eagle Mountains. The few sharply pointed, precipitous peaks which are the Seven Devils proper and have given their name to the whole group have an altitude of over seven thousand feet. They are of igneous origin and attracted the attention of prospectors many years ago, who found gold in the streams issuing from their domain and copper in the mountains adjoining them.

ore.

The only occurrence of copper of importance which has so far been exploited is found in the southern part of the range and is confined to the neighborhood of a body of whitish granitic rock of very considerable but not yet determined extent. The copper occurs as bornite and the principal mine of the locality is named the Peacock, from the nature of the The igneous rock, which evidently has a genetic relation to the copper deposits, has the general appearance of a granite and has always been so called. It is grayish white in color, and in hand specimens does resemble a biotite granite without muscovite. It weathers into rounded blocks which are sometimes met with in isolated groups, and at one point on the wagon road leading up from the Snake River to the copper mines, and about a mile from the latter, the head of a small ravine is filled with bowlders of this rock several feet in diameter which give the appearance of having been purposely rolled into the place. Water runs down among these rocks at some distance out of sight.

The whitish rock, where exposed, and in the bowlders, is seen to contain areas of a darker color which vary in size from two or three inches to as many feet in diameter and impress one at first as being inclusions of some other rock.

This igneous rock, one would say, was evidently the cause, if not the source, of the copper deposits found on its contact and in veins in its substance, and it became a matter of curiosity to examine its mineralogical and chemical character. Specimens were, accordingly, procured from points about a

mile and a half apart, one on the wagon road leading to the mines (at the White Monument hill), and the other at the Victoria mine on the northern limit of the mines where the mountain descends abruptly to form one side of Deep Creek cañon. The slightly darker appearance of the rock at the latter place indicates that its composition varies somewhat from point to point. It is also an assumption that the whole mass is continuous for the distance mentioned. Indeed a flow of basalt intervenes at one place, but the extent of the flow is undetermined.

The thin sections from these specimens show that the rock has the following structure and composition. The structure is that of granite. The stout, tabular, triclinic feldspars largely predominate. Many of them are turbid. Interstitial quartz is present. The ferromagnesian minerals are hypidiomorphic, green, pleochroic hornblende, and some brown biotite, also limited by the adjoining feldspars. Apatite crystals, zircons, and some isometric granules of ore were also observed. A section from one of the inclusions described above showed the same mineralogical composition as the lighter-colored rock but the structure shows cataclastic areas. Green hornblendes, with inclusions, and triclinic feldspars, appear in the midst of the comminuted crystals. The section also shows biotite, with inclusions, limited by the adjoining feldspars, and the ore particles are much more numerous than in the lighter-colored rock. Zonal structure of the feldspars was noticeable in both

sections.

The rock, therefore, as shown by these sections, is a diorite. Its analysis gave:

The analysis, although only partial, is sufficient to show the basic character of the rock; and the excess of soda over potash, together with the high percentage of lime, confirms the microscopical determination of the predominance of the soda-lime feldspars over orthoclase.

The specimen from the Victoria mine was taken within a foot or two of a copper vein (bornite), and the section, viewed without the analyzer, shows fissures stained bluish-green by