ox METHODS OF DETERMINING THE DRYNESS OF STEAM, 407 



5 is ai 

 limited time. 



This is an approximate value of the maximum concentration in un- 

 aited time. A second approximation to x is 



Mr. Escher has not directly suggested how his method could be used 

 in the case of a boiler fed with pure feed water, or, say, with water con- 

 taining too small an amount of chloride to give a sufficiently rapid 

 concentration. But it might easily be applied by pumping in with the 

 feed, at intervals of an hour, a known quantity, w, of a saturated salt 

 solution. The quantity w might be so arranged that the concentration 

 at the end of the test was such that the boiler water contained about 

 1 per cent, of salt. A preliminary assumption as to the amount of 

 priming would have to be made in settling what quantity of salt to 

 introduce. 



The salt method by measuring the decrease of saltness of the boiler 

 •water was first used at Mulhouse in 1859. In the trials then it failed to 

 «ive satisfactory results. In some of the tests an apparent increase of 

 saltness of the boiler water was found, which must have been due to the 

 saltness being ununiformly distributed in the boiler. At Diisseldorf in 

 1880 the method of measuring the salt in the steam was tried, sulphate 

 of soda being used.' Ten samples of boiler water and condensed steam 

 were taken in each test. The results were discrepant, giving 0-21 to 

 9 per cent, of moisture in the steam in difierent tests. 



Use of the Salt Method in the Berlin Trials of Portable Engines in 

 ]^883. — The most careful tests by the salt method which have been found 

 are some made by Dr. Bunte in Munich, in some trials of portable engines 

 under the direction of a commission appointed by the German Govern- 

 ment. ^ In these tests both the decrease of saltness of the boiler water 

 and the amount of salt in samples of condensed steam were determined. 

 They throw some light, therefore, on the relative trustworthiness of the 

 two proceedings. 



Concentrated salt solution was introduced into the boilers before 

 beginning a test till the boiler water contained 1 to 1^ per cent, of salt. 

 At the beginning of each trial, and with the water at normal level in the 

 gauge glass, a sample of boiler water was taken ; at some intermediate 

 times, and at the end of the trial, similar samples were taken. The 

 boiler water was taken from a gauge cock. To prevent evaporation in 

 taking the sample it was drawn off through an india-rubber tube into a 

 vessel containing 500 c.c. of cold distilled water. Exactly 500 c.c. of 

 boiler water were drawn off, so that the sample had half the saltness of 

 the boiler water. The chlorine was determined by a nitrate of silver 

 solution containing 10 per cent, of normal solution, with the addition of 

 «hromate solution as an indicator. For the steam samples the steam was 

 taken from a cylinder or valve-chest cock. From 200 to 1,000 grams 

 •were condensed at intervals of about an hour. 



In Trial I., on the Dolberg Portable, the boiler-water samples showed 

 the same saltness at the beginning and end of the test. Intermediate 

 samples showed very slight variations, attributed by Dr. Bunte to varia- 

 tions of water level in the boiler. In five samples of condensed steam 



* Untersuclmngen von Dampfmascldnen u.s.w. der Gewerhe-Ausstellung in Diissel- 

 dorf, 1880 (Aachen, 1881), p. 13. 



2 Report by F. Schotte, Civilingeniewr, 1884. 



