Rosin is the residuum remaining after distillation of spirits of turpentine from the crude oleo-resin exuded by several species of the pine, which abound in America, particularly in North Carolina, and also flourish in France and Spain. The gigantic forests of the United States consist principally of the long-leaved pine, _Pinus palustris (Australis)_, whilst the French and Spanish oleo-resin is chiefly obtained from _Pinus pinaster_, which is largely cultivated. Rosin is a brittle, tasteless, transparent substance having a smooth shining fracture and melting at about 135 deg. C. (275 deg. F.). The American variety possesses a characteristic aromatic odour, which is lacking in those from France and Spain. It is graded by samples taken out of the top of every barrel, and cut into 7/8 of an inch cubes, which must be uniform in size--the shade of colour of the cube determines its grade and value. The grades are as follows:-- W. W. (Water white.) W. G. (Window glass.) N. (Extra pale.) M. (Pale.) K. (Low pale.) I. (Good No. 1.) H. (No. 1.) G. (Low No. 1.) F. (Good No. 2.) E. (No. 2.) D. (Good strain.) C. (Strain.) B. (Common strain.) A. (Common.) Unsaponifiable matter is present in rosin in varying amounts. Below are a few typical figures taken from a large number of collated determinations:-- ________________________________________________________________ | | | | | | | | Saponification | Total | Free | Iodine | | | Equivalent. | Acid No. | Acid No. | No. | |________________|________________|__________|__________|________| | | | | | | | American W. W. | 330.5 | 169.7 | 119.1 | 126.9 | | American N. | 312.3 | 179.6 | 161.4 | 137.8 | | French | 320.5 | 175 | 168 | 120.7 | | Spanish | 313.4 | 179 | 160 | 129.8 | |________________|________________|__________|__________|________| ALKALI (CAUSTIC AND CARBONATED). The manufacture of alkali was at one time carried on in conjunction with soap-making, but of late years it has become more general for the soap manufacturer to buy his caustic soda or carbonated alkali from the alkali-maker. Although there are some alkali-makers who invoice caustic soda and soda ash in terms of actual percentage of sodium oxide (Na_{2}O), it is the trade custom to buy and sell on what is known as the English degree, which is about 1 per cent. higher than this.