--------------------------+------------------+----+----+----+----+---- Analyst. | Material. | C | H | N | O | S --------------------------+------------------+----+----+----+----+---- Stohmann and Langbein | .. |49·9| 5·8|18·0|26·0| 0·3 | | | | | | Müntz |Ox-hide |51·8| 6·7|18·3|23·2| .. | | | | | | |{Ox, calf, horse,}| | | | | Von Schroeder and Paessler|{camel, pig, }|50·2| 6·4|17·8|25·4| .. |{rhinoceros }| | | | | „ |Goat and deer |50·3| 6·4|17·4|25·9| .. „ |Sheep and dog |50·2| 6·5|17·0|26·3| .. „ |Cat .. .. |51·1| 6·5|17·1|25·3| .. --------------------------+------------------+----+----+----+----+---- ANALYSES OF GELATIN (free from Ash). --------------------------+----+----+----+---- Analyst. | C | H | N | O --------------------------+----+----+----+---- Von Schroeder and Paessler|51·2| 6·5|18·1|24·2 Mulder |50·1| 6·6|18·3|25·0 Fremy |50·0| 6·5|17·5|26·0 Schützenberger |50·0| 6·7|18·3|25·0 Chittenden and Solly[23] |49·4| 6·8|18·0|25·1 --------------------------+----+----+----+---- [23] Contained also 0·7 sulphur. Journ. Physiol., xii. p. 23. It will be noted that the above analyses of skin differ more widely among themselves than their average does from that of the gelatin analyses, though on the whole the nitrogen is somewhat higher in the latter. The molecular weight of gelatin must be very high,[24] and any empirical formula founded on ultimate analysis therefore quite hypothetical. Bleunard,[25] Schützenberger and Bourgois,[26] and Hofmeister agree on the formula C₇₆H₁₂₄N₂₄O₂₉, which leads to the following percentage composition:-- per cent. C₇₆ = 912 = 49·7 H₁₂₄ = 124 = 6·8 N₂₄ = 336 = 18·3 O₂₉ = 464 = 25·2 ---- ----- 1836 100·0 [24] Paal (Berichte D. Ch. Ges., xxv. (1892) pp. 1202-36, and Ch. Soc. Abst., 1892, pp. 895-7) calculates a molecular weight of about 900 from physical (freezing, boiling point) methods. [25] Annales de Chimie [5] xxvi. p. 18. [26] Compt. Rend., lxxxii. pp. 262-4. The addition of a molecule of water would make a difference in the percentage composition indicated by these formulæ which would be less than their probable experimental error, and the change may therefore be one of hydration. Gelatin certainly contains both carboxyl and amido-groups, and is capable of combining with both acids and alkalies (see p. 84).