962 Proceedings of the Royal Society 
in the case of hydrochloric acid a weight of 36 '5, in the case of 
sulphuric acid 98. Lithium chloride, molecular weight 42*5, and 
potassium sulphate, molecular weight 14 ’4, are saline. Many other 
examples might he adduced from hitter and sweet compounds to 
demonstrate that we cannot tell by the molecular weight alone any- 
thing about the taste of a substance. In the above example an acid 
may have a lower or a higher molecular weight than a salt. 
We shall see hereafter that molecular weight is not without its 
importance, and even at this stage of our inquiry it may be well to 
allude to a series of facts in this relationship. Bodies which have 
the greatest molecular weight of any, such as albumens, albumen- 
oids, starches, gums, &c., are totally without taste ; nor need it be 
urged that a ready explanation of this is at hand. No doubt many 
of these substances are not readily miscible in water, and in conse- 
quence they will not readily permeate the viscous layer of saliva 
covering the tongue and the surface of the gustatory end-organs. 
Some albumens, such as serum and egg-albumen, are fairly soluble, 
and they may all be converted by appropriate ferments into allied 
products called peptones, which are soluble and readily diffusible, 
and nevertheless devoid of taste. In like manner starch may be 
converted into dextrine, a substance readily diffusible in water, and 
tasteless. 
We find also among the list of tasteless bodies all those of very 
small molecular weight. Water, molecular weight 18, is an example. 
The simple gases dissolved in water are tasteless, but when we 
examine a substance with a molecular weight over 30, we find that 
when dissolved in water it is capable of producing some taste or 
other. Sulphuretted hydrogen, molecular weight 34, is very slightly 
acid to the taste; hydrochloric acid, molecular weight 36'5, is very 
acid ; and nitrogen monoxide, molecular weight 46, is sweet. It 
is true that the monatomic alcohols, such as ordinary commercial 
alcohol, have molecular weights over 34, and are tasteless, so that 
the same rule does not apply to all the carbon compounds ; but even 
here we are struck with the fact that these alcohols are the lowest 
of a series, all the polyatomic and more complex alcohols being 
sapid and sweet in character. 
There seems then to be some analogy between taste on the one 
hand and sight and hearing on the other. The substances of lowest 
