CO.MI'OIXDS OF CAR] JON WITH oXYdKX AND MTI.'ndKN 377 



from the former, is an example of the energetic or strong acids (such as 

 nitric or hydrochloric), whilst in carbonic acid we observe but feeble 

 development of the acid properties ; hence carbonic acid must be con- 

 sidered <> iri'cik acid. This conception must, however, betaken as only 

 comparative, as up to this time there is no definitely established rule for 

 measuring the energy 14 of acids. The feeble acid properties of carbonic 



or CO(OH).,, and other bibasic acids decompose into the anhydride, BO, and water, 

 H. 2 O. But as nitrous, HNO.,, iodio, HIO,-, hypochlorous, HC1O, and other monobasic 

 acids easily give their anhydrides X..O-, I.,O r) , CLO, &c., that method of distinguish- 

 ing the basicity of acids, although it fairly well satisfies the requirements of organic 

 chemistry, must not be considered correct. It may also be remarked that up to the present 

 time not one of the bibasic acids has been found to have the faculty of being distilled with- 

 out being decomposed into anhydride and water (even H 2 SO 4 , on being evaporated and 

 distilled, gives SO- + H.,O), and the decomposition of acids into water and anhydride pro- 

 ceeds particularly easily in dealing with feebly energetic acids, such as carbonic, nitrous, 

 boric, and hypochlorous. Let us add that carbonic acid, as a hydrate corresponding to marsh 

 gas, C(HO)4 = CO.) + 2H.,O, ought to be tetrabasic. But in general it does not form such salts. 

 Basic salts, however, such as CuCO 3 CuO, may be regarded in this sense, because CCu. 2 O 4 

 corresponds with CH^O.^, as Cu corresponds with Ho. Amongst the ethereal salts (alco- 

 holic derivatives) of carbonic acid corresponding cases are, however, observed ; for 

 instance, ethylic orthocarbonate, C(CoH 5 O) 4 (obtained by the action of chloropicrin, 

 C(NO.,)C1 3 , on sodium ethoxide, C.,H 5 ONa; boiling point, 158; specific gravity, 0'92). 

 The name orthocarbonic acid for CH 4 O 4 is taken from ortliophosplioric acid, PH 3 O 4 , 

 which corresponds with PH 3 (see Chapter on Phosphorus). 



K Long ago endeavours were made to find a measure of affinity of acids and bases, 

 because some of the acids, such as sulphuric or nitric, form comparatively stable salts, de- 

 composed with difficulty by heat and water, whilst others, like carbonic and hypochlorous 

 ticids, do not combine with feeble bases, and with many form salts which are easily decom- 

 posed. The same may be said with regard to bases, among which those of potassium, K.>O, 

 sodium, Na 2 O, and barium, BaO, may serve as examples of the most powerful, because 

 they combine with the most feeble acids and form a mass of salts of great stability, whilst 

 as examples of the feeblest bases alumina, A1 2 O 3 , or bismuth oxide, BioO 3 , may be taken, 

 because they form salts easily decomposed by heat and water if the acid be volatile. 

 Such a division of acids and bases into the feeblest and most powerful is justified by all 

 evidence concerning them, and is quoted in this work. But in recent years the teaching 

 of this subject has acquired quite a new tone, which, in my opinion, cannot be accepted 

 without certain reservations and remarks, although it comprises many interesting features. 

 The fact is that Thomsen, Ostwald, and others proposed to express the measure of affinity 

 of acids to bases by figures drawn from data of the measure of displacement of acids in 

 aqueous solutions, judging (1) from the amount of heat developed by mixing a solution 

 of the salt with a solution of another acid (the avidity of acids, according to Thomsen) ; 

 (2) from the change of the volumes accompanying such a mutual action of solutions 

 (Ostwald) ; (3) from the change of the index of refraction of solutions (Ostwald), &c. 

 Besides this there are many other methods which allow us to form an opinion about the 

 distribution of bases among various acids in aqueous solutions. Some of these methods 

 will be described hereafter. It ought, however, to be remarked that in making investiga- 

 tions in aqueous solutions the affinity to water is generally left out of sight. If a base N, 

 combining with acids X and Y in presence of them both, divides in such a way that one- 

 third of it combines with X and two-thirds with Y, a conclusion is formed that the affinity, 

 or power of forming salts, of the acid Y is twice as great as that of X. But the presence 

 of the water is not taken into account. If the acid X has an affinity for water and for N 

 it will be distributed between them ; and if X has a greater affinity for water than Y, 

 then less of X will combine with N than of Y. If, in addition to this, the acid X is 



