20 



DR. BASTIAJ^ ON THE 



Subsequently the end of tube is bent, in the manner shown in the 

 figure (c), and then hermetically sealed. 



Thus prepared, the tube should be just half full of liquor po- 

 tasssB. Its length will have been diminished as much as possible ; 

 and its tip is so arranged that it may be easily broken off by a 

 slight mechanical shock. These last steps in the preparation of 

 the liquor-potassse tubes are best carried out with the aid of a 

 very small spirit-lamp flame, as they require to be done slowly 

 and with care. On the one hand, it is necessary that the bent 

 part of the tube should be weak enough to break readily when 

 jerked against the wall of the experimental vessel in which it is 

 afterwards enclosed ; and, on the other, it must not be so much 

 weakened as to make it break too easily or be unable to bear the 

 internal strain which it will have to undergo during its immer- 

 sion in boiling water. This, in fact, is the final stage in the pre- 

 paration of the liquor-potassse tubes. A number of them, after 

 they have been hermetically sealed, are to be placed in a suitable 

 vessel containing warm water ; and they are then to be raised to 

 the temperature of 212° F. (100° C.) for the period fixed upon. 

 As in these experiments I soon found that the longer or shorter 

 duration of the period of boiling of the liquor-potassse tubes 

 did not appreciably influence the results, they were, for the most 

 part, boiled for 15"-20" only — though in many cases it was much 

 longer, and in two or three they were boiled for 2 hours. Thus 

 prepared, the tubes were set aside in compartments labelled ac- 

 cording to the number of minims of liquor potassae which they 

 contained. 



A stock of such tubes being ready to hand, experiments may 

 be made at any time. A suitable specimen of fresh urine is to be 

 taken, whose specific gravity is to be ascertained and whose degree 

 of acidity is to be most carefully estimated. This latter process 

 I have carried out by taking exactly 1 fluid-ounce of the urine 

 and adding liquor potassae to it, minim by minim, from the burette- 

 tube till the point of saturation is nearly reached. Thereafter 

 the alkali has been added in half-minims at a time, and tested 

 between each addition with litmus and turmeric paper so as to 

 make quite sure of the time of complete neutralization*. In order 



* It is not unimportant here to add that the test-papers which I have used 

 have been those sold by Mr.W. Martindale, of 10 New Cavendish Street, London. 

 They are similar to the papers used in the wards of University-College Hos- 

 pital. By careful trial I have ascertained that ^ of a minim of liquor po- 



