The blocks are oblong, one-fourth of an inch thick, the ends (c c, [Fig. 112]) beveled, the sides either beveled or straight, the latter preferable. They vary in length and breadth according to the different sizes of the vials, and are painted white. Upon the upper side of these blocks are fastened two curved clamps of music wire (b b), forming about two-thirds of a complete circle. The fastening to the block is simple and secure. A bit of the wire of proper length is first doubled and then by a special contrivance the two ends are bent around a mandrel so as to form an insertion point or loop. A brad awl is used to make a slot in the block, into which this loop is forced (e, [Fig. 112], 5), a drop of warm water being first put into the slot to soften the wood, which swells and closes so firmly around the wire that considerable force is required to pull it out. Four pointed wire nails (d d d d), set into the bottom so as to project about one-fourth inch, serve to hold the block to the cork bottom of the case or drawer in which it is to be placed. The method of use is simple and readily seen from the accompanying figures, which represent the block from all sides.
The advantages of this system are the ease and security with which the block can be placed in or removed from a box; the ease with which a vial can be slipped into or removed from the wire clamps; the security with which it is held, and the fact that practically no part of the contents of the vial is obscured by the holder—the whole being visible from above.
The beveled ends of the block may be used for labeling, or pieces of clean cardboard cut so as to project somewhat on all sides may be used for this purpose, and will be held secure by the pins between the block and the cork of the drawers.
Fig. 112.—Vial holder; 1, block, with vial, beveled on all sides; 2, do., beveled only on ends; 3, block, end view; 5, do., section; 4, 6, do., side views; a, block; b, spring-wire clamps; c, beveled ends of block; d, pointed wire nails; e, point of insertion of clamp. (Lettering on all figures corresponds.)
The use of rubber stoppers in this country was first instituted by Dr. H. A. Hagen in connection with the Cambridge biological collection, and he has made some very careful records to determine the durability of such stoppers. From an examination of some seven thousand vials with rubber stoppers, two-thirds of which had been in use for from ten to twelve years, he comes to the conclusion that less than one in a thousand gives out every year after twelve years' use, and in the first six years probably only one out of two thousand. Stoppers of large size keep much longer than those of small size. American rubber stoppers are all made of vulcanized India rubber and have the disadvantage of forming small crystals of sulphur about the stopper, which become loosened and attach themselves to the specimens. It is supposed that pure rubber-stoppers used for chemical purposes would not present this disadvantage, which may be obviated, however, or very much reduced, if the stoppers are washed or soaked, preferably in hot water, for an hour or two at least.
If stoppers are stored for a considerable time and exposed to the air they become very hard and unfit for use, and Dr. Hagen has drawn attention to a method recommended by Professor W. Hemple, of Dresden, Saxony, of preventing them from becoming thus hardened. He says that to keep rubber stoppers or rubber apparatus of any sort elastic, they should be stored in large glass jars in which an open vessel containing petroleum is placed. This treatment prevents the evaporation of the fluids which are fixed in the rubber in the process of vulcanization. It is better also to keep the light from the jar. To soften stoppers which have already become hardened, they should be brought together in a jar with sulphuret of carbon until they are pliable and afterward kept as recommended above.
In the use of the rubber stopper the novice may find some difficulty in inserting it in a vial filled with alcohol. The compression of the alcohol, or alcohol and air when the vial is not completely filled, forces the stopper out, and this is true whether of rubber or cork. If a fine insect pin is placed beside the cork when this is thrust into the bottle, the air or liquid displaced by the cork will escape along the pin and the latter may then be removed and the cork remains securely in position.
If cork stoppers have been used the vials may be stored in large quantities together in jars filled with alcohol. This will prevent evaporation of the alcohol from the vials, and the specimens may be preserved indefinitely. This is only desirable in the storage of duplicate specimens and unarranged material and is not recommended as a substitute for the use of the rubber stopper. With cork stoppers evaporation can be in a measure prevented if the cork is first anointed with the petroleum preparation known as vaseline. This substance is practically unaffected at ordinary temperature and is sparingly soluble in cold alcohol. Experiments with it have shown that at ordinary spring and summer temperatures there is no appreciable loss of alcohol from vials and jars.