208 Mr. S. Holker on Dr. Dalton's new Method of 



the ingenuity by which all his researches have been charac- 

 terized, should have excited so little attention among men of 

 science. The law which he attempted to establish would be 

 highly valuable if it could be confirmed, and if not correct it 

 must be desirable that its fallacy should be demonstrated. 

 Under this impression I have undertaken to repeat and ex- 

 tend his experiments. The law which Dr. Dalton gives rela- 

 tive to the combination of salts and water is, that when a salt 

 dissolves it will only increase the volume in proportion to the 

 water of crystallization it contains. 



The method by which Dr. Dalton ascertains the water of 

 crystallization in salts is as follows: — "I have," he observes, 

 "a bottle with a stopper which just contains 572 grains of 

 pure water, when the stopper is put in and wiped clean and 

 dry at the temperature of 60° F. ; a graduated tube or jar is 

 necessary, about six inches long and one quarter of an inch 

 in diameter, to measure exactly to a grain of water." In using 

 this apparatus, " the bottle is first filled with water at the tem- 

 perature of 60° F. and wiped clean and dry ; the water in the 

 bottle is then carefully transferred into a vessel of larger di- 

 mensions, and a known weight of the salt to be tried is dis- 

 solved in the fluid ; the solution of salt is then carefully trans- 

 ferred into the bottle, and the spare liquor, if any, is put into 

 the graduated tube." 



Now it is evident that this apparatus of Dr. Dalton is not 

 susceptible of the requisite precision and nicety of manipula- 

 tion ; for in transferring the solution of salt from the vessel of 

 larger dimensions into the bottle and graduated tube, there 

 will be a loss owing to the cohesion of the water to the glass, 

 so that the error will be very considerable when a sparingly 

 soluble salt is used. 



In prosecuting a research of so much interest and import- 

 ance, I found it necessary to use much more delicate appa- 

 ratus than that employed by Dr. Dalton, as it was desirable 

 to obtain for the establishment or subversion of a law as ac- 

 curate results as possible. In order to effect this purpose, I 

 procured a tube about six inches long and a quarter of an inch 

 in diameter, with a bulb blown at one end, which when full 

 up to a certain mark on the stem, held exactly 430 grains of 

 pure water. From this mark upwards the tube was divided 

 into 100 grain measures, so that when full up to the highest 

 mark it held exactly 530 grains of pure water. 



In order to experiment with this apparatus, I first filled 

 the bulb and stem to the lowest mark with water, and after- 

 wards added a known weight of salt, carefully noting the in- 

 crease of bulk. 



