Royal Society. 47 



quality will yield four gallons of oxygen gas, and that this is about 

 "the maximum obtainable quantity." But the author states that 

 1638 grains of peroxide of manganese yield 200 grains of oxygen gas, 

 consequently 7000 grains, or one pound, will give 854 grains ; then as 

 34"4 grains occupy 100 cubic inches, 854 grains will give 2482 cubic 

 inches, which divided by 277 \3, the cubic inches in a gallon will give 

 8-^ gallons of oxygen gas. Of course this is supposing the per- 

 oxide of manganese to be pure ; but even if the impurity amounts to 

 50 per cent., the quantity of oxygen will be greater than that stated 

 as the maximum obtainable from peroxide of " good quality." 



Mr. Noad also states that the 1438 grains of oxide left after 

 heating 1638 grains of peroxide of manganese is " a mixture of 992 

 grains of deutoxide and 446 grains of protoxide of manganese." The 

 fact however is that the 1438 grains are red oxide of manganese, 

 which are certainly equivalent to, but are not a mixture of, the two 

 oxides named, for deutoxide cannot exist at the temperature re- 

 quisite to produce 1438 grains of red oxide from the stated quantity 

 of peroxide. 



Several errors occur in the author's statements respecting the 

 production of oxygen gas from chlorate of potash : we are informed 

 that half an ounce (218*75 grains) should yield 270 cubic inches of 

 oxygen gas, he having just before stated 1532 grains yield 600 grains 

 of oxygen, 218*75 therefore give 85 - 7 grains, measuring only 249 

 instead of 270 cubic inches. 



The following note on this subject at p. 144, exhibits an extraor- 

 dinary degree of confusion of per-centage, weight and measure : — " I 

 find that the best chlorate of potash yields from 96 to 98 per cent, 

 of pure oxygen." For some time we were puzzled to attach any 

 meaning to this statement, but at length we concluded that the fol- 

 lowing is what the author meant : — " I find that 100 grains of the 

 best chlorate of potash yield from 96 to 98 cubic inches of pure 

 oxygen gas." 



Confusion of a somewhat similar kind, though not quite so glaring, 

 is observable in the following statement : " from an equivalent of 

 the oxide [of mercury] we get 100 grains, or nearly 300 cubic inches 

 of oxygen gas, and 1266 grains of mercury are found in the re- 

 ceiver." It should have been stated that from 1366 grains, which 

 may be considered as representing an equivalent: but according to the 

 author's method equivalents are not relative merely, but absolute 

 weights. 



We had noted many other statements contained in this work for 

 observation, but the length to which this notice has extended pre- 

 cludes our further proceeding. 



XI. Proceedings of Learned Societies. 



ROYAL SOCIETY. 

 [Continued from vol. xxii. p. 490.] 

 Feb. 23, r I ^HE following papers were read, viz. — 



1843. ■*• 1. " Researches on the Decomposition and Disinte- 

 gration of Phosphatic Vesical Calculi ; and on the introduction of 



