The biological examination of water / by C.J.H. Warden.

  • Warden, Charles James Hislop, 1851-1900.
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: The biological examination of water / by C.J.H. Warden. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    which should be heated to 150° to 160° C. for one hour and a-half. This temperature slightly browns the plugs, and is sufficiently high to destroy any germs which may have adhered to the interior of the tubes or to the plugs. After the lapse of the prescribed time the burner should be extinguished, and the tubes allowed to cool in the oven with the door closed: when cold they can be removed from the cage and preserved in a box, care being taken to avoid disturbing the plugs. Pipettes to hold 1, 2, and 3 c.c., and also to hold 1 c.c., divided into one-tenth and one-fifth of a c.c., are used to measure the water. They are sterilised by being heated in the air-bath to 150°—i6o°C. for one hour and a half, and are then allowed to cool in it, and removed for use as required. Several pipettes should be provided, as a freshly sterilised one is requisite for each sample of water tested. It must be remembered that a pipette once sterilised will not remain germ-free for any time, though not removed from the bath in which it has been heated. The most convenient procedure is to daily heat the requisite number of pipettes required. Glass ro/ts of about 2 c.m. in length are used for spread- ing the liquefied gelatin on the plates, &c. They are sterilised in the same manner and at the same time as the pipettes. Glass plates of flat crown-glass free from flaws, 13 x 10 c.m. in size, are used for receiving the gelatin film. The sharp edges should be ground down, and the plates then care ully freed from grease, rinsed with hydrochloric acid, and thoroughly washed. When dry they are placed in a copper or sheet-iron box (Fig. 3) provided with a tightly- fitting cover, which is closed, and the box heated in the air-bath for two hours to 1500—i6o°C. When cold the box is removed from the bath, and provided care betaken in the removal of a plate the glasses will remain fit for use for several days. In removing a glass plate the box should be held horizontally, a plate slipped out, and the cover at once re- placed. If a plate has not been recently sterilised it is advisable to again heat it, by holding one corner with a pair of crucible tongs, and rapidly passing both sides several times through a flame, so as to thoroughly heat every part. It is then placed under a bell-jar to cool, supported on a beaker or other convenient support. A waim plate must never be placed on the levelling appa- ratus (Fig. 7) or it is almost certain to crack. Dr. H. Rohrbeck, of 100, Friedrich-strasse, Berlin, manufadlures glass plates, with a slightly raised square ridge in the centre, 9x9 c.m., into which the gelatin,