Methods and apparatus for visualising a print on an object

1. A method for production of a metal halide product of S 4 N 4 comprising the steps of:

a. reacting S 2 Cl 2 with gaseous ammonia in a dry solvent to produce crude S 4 N 4 ;

b. without purification, adding the crude S 4 N 4 to a solution of metal halide in alcohol and stirring until no S 4 N 4 remains; and

c. obtaining the metal halide product of S 4 N 4 by removal of the alcohol.

2. The method of claim 1 , wherein the metal halide is CuBr 2 , and the metal halide product of S 4 N 4 is CuBr·S 4 N 4 .

3. The method of claim 1 , wherein the dry solvent is carbon tetrachloride or tetrachloroethylene.

4. The method of claim 1 , wherein the alcohol is methanol.

5. The method of claim 1 , wherein step (a) is conducted at a temperature of less than about 100° C.

6. The method of claim 1 , wherein step (b) is conducted at a temperature of from about 40° C. to about 60° C.

7. A method for visualising a print on an object comprising

a. placing within an apparatus:

i. the object potentially comprising at least one print; and

ii. a metal halide product of S 4 N 4 produced by a process comprising:

reacting S 2 Cl 2 with gaseous ammonia in a dry solvent to produce crude S 4 N 4 ;

without purification, adding the crude S 4 N 4 to a solution of metal halide in alcohol and stirring until no S 4 N 4 remains; and

obtaining the metal halide product of S 4 N 4 by removal of the alcohol;

b. heating the metal halide product of S 4 N 4 under vacuum to produce S 2 N 2 vapour;

c. cooling the S 2 N 2 vapour at or in proximity to the object to promote a phase change to solid S 2 N 2 ; and

d. heating the solid S 2 N 2 back to S 2 N 2 vapour to facilitate interaction of the S 2 N 2 vapour with the object to visualise the print.

8. The method of claim 7 , wherein, in step (b), the metal halide product of S 4 N 4 is heated to from about 160° C. to about 170° C.

9. The method of claim 7 , wherein, in step (c), the S 2 N 2 vapour is cooled to a temperature of from about 25° C. to about 0° C.

10. The method of claim 7 , wherein, in step (d), the solid S 2 N 2 is heated to generate S 2 N 2 vapour at a temperature of from about 25° C. to about 50° C.

11. The method of claim 7 , wherein the object is contacted with the S 2 N 2 vapour for at least 1 to 15 minutes.

12. The method of claim 7 , wherein the vacuum is at a pressure of from about 1.33×10 −6 Pa to about 133 Pa.

13. The method of claim 7 , wherein, in step (b), the metal halide product of S 4 N 4 is heated to from about 155° C. to about 170° C.

14. The method of claim 7 , wherein, in step (c), the S 2 N 2 vapour is cooled to a temperature of from about 25° C. to about −5° C.

15. The method of claim 7 , wherein, in step (d), the solid S 2 N 2 is heated to generate S 2 N 2 vapour at a temperature of from about 25° C. to about 65° C.

16. The method of claim 1 , further comprising forming at least a part of the metal halide product of S 4 N 4 into a pellet.

17. The method of claim 16 , wherein an excipient is provided when forming the at least the part of the metal halide product of S 4 N 4 into the pellet.

18. The method of claim 17 , wherein the excipient comprises microcrystalline cellulose or polyvinylpyrrolidone.

19. A method for visualising a print on an object comprising

a. placing within an apparatus:

i. the object potentially comprising at least one print; and

ii. a metal halide product of S 4 N 4 ;

b. heating the metal halide product of S 4 N 4 under vacuum to produce S 2 N 2 vapour;

c. cooling the S 2 N 2 vapour at or in proximity to the object to promote a phase change to solid S 2 N 2 ; and

d. heating the solid S 2 N 2 back to S 2 N 2 vapour to facilitate interaction of the S 2 N 2 vapour with the object to visualise the print.