Very far from it; it is only certain substances which will enter into that peculiar kind of union with oxygen that produces acids, and the number of these is proportionally very small; but all burnt bodies may be considered as belonging either to the class of oxyds, or to that of acids. At a future period, we shall enter more at large into this subject. At present, I have but one circumstance further to point out to your observation respecting acids: it is, that most of them are susceptible of two degrees of acidification, according to the different quantities of oxygen with which their basis combines. EMILY. And how are these two degrees of acidification distinguished? MRS. B. By the peculiar properties which result from them. The acid we have just made is the first or weakest degree of acidification, and is called _sulphureous acid_; if it were fully saturated with oxygen, it would be called _sulphuric acid_. You must therefore remember, that in this, as in all acids, the first degree of acidification is expressed by the termination in _ous_; the stronger, by the termination in _ic_. CAROLINE. And how is the sulphuric acid made? MRS. B. By burning sulphur in pure oxygen gas, and thus rendering its combustion much more complete. I have provided some oxygen gas for this purpose; it is in that bottle, but we must first decant the gas into the glass receiver which stands on the shelf in the bath, and is full of water. CAROLINE. Pray, let me try to do it, Mrs. B. MRS. B. It requires some little dexterity--hold the bottle completely under water, and do not turn the mouth upwards, till it is immediately under the aperture in the shelf, through which the gas is to pass into the receiver, and then turn it up gradually. --Very well, you have only let a few bubbles escape, and that must be expected at a first trial. --Now I shall put this piece of sulphur into the receiver, through the opening at the top, and introduce along with it a small piece of lighted tinder to set fire to it. --This requires being done very quickly, lest the atmospherical air should get in, and mix with the pure oxygen gas. EMILY. How beautifully it burns! CAROLINE. But it is already buried in the thick vapour. This, I suppose, is sulphuric acid? EMILY. Are these acids always in a gaseous state? MRS. B.