290 Mr. Griffin on the Constitution of 



phates, the arseniates, the oxalates, the citrates, the tartrates, 

 the acetates, &c. &c, and have been uniformly successful. 

 Only the water adds to the bulk and the solid matter adds to 

 the weight/' — Essay on the quantity of Acids, Bases and 

 Water in the different varieties of Salts ; with a new method 

 of measuring the Water of Crystallization, as well as the 

 Acids and Bases. 



Dr. Dalton knew well the importance of the principle he 

 was attempting to establish, lor he declares "It is the 

 greatest discovery that 1 know of next to the atomic theory." 

 — New and Easy Method of Analysing Sugar. 



In May 1845, Messrs. Playfair and Joule presented to the 

 Chemical Society a memoir, in Mhich they have recorded the 

 results of an elaborate experimental examination of Dalton's 

 hypothesis. (See Philosophical Magazine, vol. xxvii. p. 453.) 

 Their conclusions are no less startling than were those of 

 Dalton, on which the inquiry proceeded. They find his doc- 

 trine in relation to sugar to be true. " It is," they say, " an 

 extraordinary fact, that the twelve atoms of carbon in sugar 

 cease to occupy space in solution, and that the bulk of an 

 atom of sugar is just the bulk of its oxygen and hydrogen 

 considered as water. And this," they say, " is a matter of 

 supreme interest, and cannot fail to lead to important results 

 when we come to the consideration of organic compounds." 

 — Pages 530 and 474. 



They next confirm Dalton' s statement with regard to sul- 

 phate of magnesia and other analogous salts, namely, that 

 when anhydrous they occupy no space in solution, but when 

 hydrated they add the bulk of the water of hydration to the 

 bulk of the water of solution. 



Thirdly, they find that other compounds dissolved in water 

 increase its volume for every equivalent, either by 9 or by 

 multiples of 9. [9 is their standard number for the volume 

 of an equivalent of water.] 



These statements affirm three main propositions, namely,-— 



1. That certain anhydrous substances when dissolved in 

 water occupy no space. The volume of the solution is the 

 same as the volume of the water contained in it. 



2. That other anhydrous substances when dissolved in 

 water assume a fixed and characteristic volume ; so that the 

 volume of the solution is not the same as that of the water 

 contained in it, but greater or smaller, in exact proportion to 

 the atomic volume of the substance dissolved in it. 



3. That when organic substances are dissolved in water 

 their carbon occupies no space, but their hydrogen and oxy- 



